Eleven leading figures from nine parties have written a joint letter questioning the CPS's decision not to prosecute Lord Janner for child abuse . Leading politicians from seven parties have come together to attack the decision not to prosecute Lord Janner over child abuse and accused the CPS of orchestrating a 'whitewash'. Putting the election aside, 11 leading figures said that Director of Public Prosecutions Alison Saunders was ‘damaging public confidence’ in the justice system with her ruling. The CPS has been accused of double standards for not prosecuting Lord Janner after it emerged at least 19 men with dementia have been convicted of child sex offences since 2010, including ten in the past year. MailOnline has revealed that some paedophiles, including several too ill to enter a plea, have still been prosecuted and in some cases jailed for the rest of their lives because of historic sex attacks. But Alison Saunders and the CPS insist Lord Janner cannot face prosecution. Politicians have written to a national newspaper to demand the decision be reversed amid public concerns. The cross-party group, led by Labour’s Simon Danczuk, asked in their letter to The Times: ‘Have we learnt anything from the mistakes of the past? ‘As long as justice is not seen to be done and the greater public interest is not served, the public will see attempts to investigate establishment figures involved in historic child abuse as a whitewash.’ Mrs Saunders announced last week that 86-year-old Labour peer Lord Janner, who has dementia, would not face trial over 22 serious offences against nine alleged victims in Leicestershire, from the 1960s to the 1980s. The intervention was co-ordinated by Mr Danczuk, who investigated the Cyril Smith abuse scandal in Rochdale and the subsequent cover-up. Mrs Saunders’ decision has already drawn criticism from Home Secretary Theresa May. Police are considering a legal challenge, and Lord Macdonald of River Glaven, a former director of public prosecutions, has also questioned the decision. Last night a former president of the Law Society said the Crown Prosecution Service had failed in its duty to put suspected wrongdoers before the courts. Simon Danczuk (left) lead the intervention, that was also backed by the likes of Tory Zac Goldsmith (right), Green MP Caroline Lucas, Ukip's Mark Reckless and John Hemming from the Liberal Democrats . Linda Lee, who now represents victims and witnesses, said: ‘Alison Saunders may well be right that Lord Janner is not fit to stand trial but it should not be a matter for her to decide. 'The matter should be brought before the courts so that the evidence may be tested in accordance with the law. ‘This case clearly demonstrates why victims of abuse feel let down by the system.’ Leicestershire Police told The Times they were concerned about alleged improper attempts by a member of the Bar to influence key legal decisions in their investigation into Lord Janner and other suspects. A spokesman said: ‘We are aware of this barrister and had concerns but were assured the CPS were dealing with this matter.’ The CPS said no improper attempts had been made to influence Mrs Saunders. A spokesman said: ‘The DPP was not unduly influenced by anyone when making this decision. As head of the CPS — an independent prosecuting authority — the DPP is used to making difficult decisions and will continue to do so independently.’ The letter accuses Director of Public Prosecutions Alison Saunders (pictured) of 'damaging public confidence'  with her ruling that Lord Janner is unfit to be prosecuted due to his Alzheimer's . A procedure exists to deal with criminal suspects thought to have mental illness. In serious cases where a judge rules a suspect is not fit to stand trial a jury can hear the evidence in the suspect’s absence and decide if the individual committed the crimes. A suspect is not found to be guilty, or not guilty, but a jury do rule on if they have committed the crimes. Often the judge will order them be detained in hospital, often indefinitely. The patient's discharge, transfer or leave of absence from hospital cannot be without the consent of the Secretary of State. Lord Janner’s family has said that the former Leicester West MP is a man of the ‘highest integrity’ who is ‘totally innocent of any wrongdoing’. The peer was found to have Alzheimer’s disease in 2009 but continued to speak in the House of Lords until December 2013. He stopped attending in the week  police searched his home in Hampstead, north London, and later took formal leave of absence. That leave was renewed this month when Lord Janner signed a letter to House of Lords clerks. The full list of signatories to The Times letter is: Mr Danczuk (Labour); John Mann (Labour); John Hemming (Liberal Democrat); Zac Goldsmith (Conservative); Nadine Dorries (Conservative); Mark Reckless (Ukip); Caroline Lucas (Green); Naomi Long (Alliance party); Jim Shannon (DUP); Sarah Wollaston (Conservative); Tessa Munt (Liberal Democrat). Case: The CPS has decided not to prosecute Lord Janner over alleged child sex offences but 19 others with dementia have been pursued in recent years . The CPS has been accused of double standards for not prosecuting Lord Janner after it emerged at least 19 men with dementia have been convicted of child sex offences since 2010, including ten in the past year. MailOnline can reveal that some paedophiles, including several too ill to enter a plea, have still been prosecuted and in some cases jailed for the rest of their lives because of historic sex attacks. On Friday Alison Saunders, Director of Public Prosecutions, concluded that former Labour MP Lord Janner's dementia made him unfit to plead on 22 historic child sex offences between 1969 and 1988. She decided there was no public interest in prosecuting Janner because of his illness, yet the CPS' latest prosecution of a dementia sufferer on sex charges came in February. Two months ago Roy Shaw, 68, was considered unfit to plead to child sex charges against him but was tried by a jury anyway for sex attacks dating back to 2013, and detained in a hospital indefinitely under the mental health act. Peter Saunders, of the National Association for People Abused in Childhood said: ‘This is certainly double standards by the CPS. Of course any right thinking person knows deep down there is a cover up here. ‘The cases MailOnline has uncovered prove that and I believe there are more. I believe he’s being protected. ‘There is unease that someone as influential and high profile as Lord Janner will not face trial when Joe Bloogs has. It is very convenient that the CPS finally admits he should have been prosecuted just a the time when they say they can’t. ‘People are worried about the beans he might spill should he be brought to trial’. In January paedophile John Hayford, 84, who has dementia and Alzheimer's, was jailed for two years for abusing a seven-year-old 20 years ago in Stanmore, London. Cases: Last year William Chamberlain, 66, left,  and Joseph Birtles, 81, right, both of whom have dementia, were told they may die in jail for abusing children and given prison sentences . He was sentenced two months after he was found guilty of sexually assaulting a girl, nine, in a supermarket. In December Swindon pensioner William Chamberlain, 66, an alcoholic with dementia, was told he may die in prison after he was found to have abused a girl from the age of five, threatening to kill her family if she told them. A judge jailed him for eight years and eight months and told him he stole the girl's innocence. Last August Joseph Birtles, 81, a retired primary school teacher who abused children as young as eight over 20 years, was convicted of 15 counts of indecent assault on seven victims. His defence team pleaded for 'mercy' because of his dementia and other illnesses but he was jailed for seven years  at the Old Bailey and told he would likely die in prison. The contrast with Janner's case has caused fury among his victims and campaigners and came as it emerged the politician, diagnosed with dementia in 2009, has claimed tens of thousands of pounds in expenses in recent years. He voted in the House of Lords 37 times in 2013 and took a formal leave of absence last October. When asked if he would consider retiring when the election was called, he responded in a personally signed letter received just three weeks ago - on April 9 - asking to continue in office. Last summer Stephen Turner, who has bipolar disorder and fronto-temporal dementia, which leads to changes in personality, was found unfit to stand trial but found to have carried out a number of child sex offences. He had performed a sex act on himself in front of children in a theme park three months after police found a cache of child porn on his computer, and was sentenced to a hospital order. Abusers: John Hayford, 84, left, who has dementia and Alzheimer's, was jailed for two years for abusing a girl 20 years ago while John Nolan, was convicted of abusing a little girl but given a suspended sentence because of his dementia . Prosecutions: Gerald Longman, now 81, left, was spared jail despite sexually and physically abusing his daughters and Canadian actor Iain Quarrier was convicted of the attempted abduction of a five-year-old girl in a busy supermarket. He has korsakoff's syndrome, a form of dementia . Last March a former director of the Ulster Museum in Belfast, John Nolan, was convicted of abusing a little girl but given a suspended sentence. His defence QC told the judge that sending his client to prison 'would be a death sentence and Judge Piers Grant agreed that although his offending deserved a prison sentence he would 'exercise considerable mercy'. In February 2014 David Massingham was deemed unfit to stand trial back in February because of his memory loss and confused state. But a jury at Teesside Crown Court still heard his case and convicted him of ten indecent assaults and an offence of a serious sexual assault committed more than 30 years ago. He was also detained in a hospital. In 2012 Gerald Longman, now 81, was spared jail despite sexually and physically abusing his daughters, who waived their anonymity to say they wished he was dead. Longman was given an absolute discharge at Taunton Crown Court as he had been deemed unfit to stand trial due to dementia - but a jury listened to the facts and ruled he had committed the crimes. In 2008 Canadian actor Iain Quarrier was convicted of  the attempted abduction of a five-year-old girl in a busy supermarket. He was given a suspended sentence and banned from unsupervised contact with children after his defence argued he was suffering from korsakoff's syndrome, a form of dementia and was also an alcoholic, but claimed he was not a paedophile.
Eleven politicians from 7 parties made comments in letter to a newspaper .
Said DPP Alison Saunders had 'damaged public confidence' in justice .
Ms Saunders ruled Lord Janner unfit to stand trial over child abuse claims .
The CPS has pursued at least 19 suspected paedophiles with dementia .