Deputy chair of the IPCC Deborah Glass said "without a shadow of a doubt" it will be the biggest ever investigation carried out into police behaviour in the UK. She told reporters: "I think I can confidently say this will be the largest independent inquiry that has been launched into the actions of the police in the United Kingdom." The report by the Hillsborough Independent Panel published last month claimed that a shocking cover-up was staged in order to shift blame onto the 96 victims. It alleged that 164 police statements were altered in the wake of the tragedy, 116 of them to remove or change negative comments about the policing of the match and the ensuing disaster. Questions have also been raised over whether manslaughter charges should be brought over the deaths. Ms Glass said: "The potential criminal and misconduct offences disclosed by the panel's report fall into two broad categories. They are the allegations that go to the heart of what happened at Hillsborough in April 1989 and individuals and institutions may be culpable for the deaths, and there are allegations about what happened after the disaster, that evidence was fabricated and misinformation was spread in an attempt to shift blame. Allegations that statements were altered and that misleading information was passed to the media and MPs will be investigated and could lead to police misconduct and criminal charges, Ms Glass said. Claims that officers questioned bereaved next of kin about their loved ones' alcohol consumption, carried out alcohol testing and checked the police national computer to find information about the dead and injured could also lead to charges. Both South Yorkshire Police, who dealt with the tragedy, and West Midlands Police, who investigated how South Yorkshire handled the disaster, will come under scrutiny. Ms Glass said: "We will investigate the role of South Yorkshire Police and West Midlands Police in these matters. This will mean that a large number of current and former officers will be under investigation, including Sir Norman Bettison, whose conduct was referred by the West Yorkshire Police Authority. Sir Norman, currently Chief Constable of West Yorkshire, has been referred to the IPCC over allegations that he provided misleading information after the tragedy. It was revealed today that he is also under investigation for allegations that he "attempted to influence the decision-making process of the West Yorkshire Police Authority in connection with the referral that they had made," Ms Glass said. West Yorkshire Police said Sir Norman had previously welcomed an investigation into Hillsborough and had nothing further to add today. A spokesman said: "Sir Norman Bettison has consistently made the point since September 15, three days after the report was published, that these were matters that needed to be investigated formally and fairly by the IPCC. At the time, he immediately welcomed the Police Authority's decision to refer this matter. He is on record as saying he is keen to co-operate with the IPCC inquiry, but now that has been launched, he has nothing further to add. Chief Constable of West Midlands Police Chris Sims said: "I welcome today's decision by the IPCC to look into the role of West Midlands Police following the tragedy at Hillsborough in 1989. As chief constable I read the Hillsborough Independent Panel Report and immediately referred West Midlands Police to the IPCC. Today, the IPCC have accepted that referral and West Midlands Police will give their full support to the IPCC investigation. Margaret Aspinall, who lost her 18-year-old son James in the tragedy and is chairwoman of the Hillsborough Families Support Group, welcomed today's announcement. She said: "I can only repeat again what we said four weeks ago, the truth is out there. I think the time is now for accountability. Commenting on the investigation of Sir Norman, Les Carter, vice-chair of West Yorkshire Police Authority, said: "The Police Authority's Special Committee met again recently and decided to voluntarily refer a conduct matter concerning the chief constable to the IPCC for an independent investigation. We will offer the Commission every assistance in what we hope will be a prompt and proportionate investigation, but we do not think it is appropriate to elaborate further as we don't want to prejudice it in any way. Liverpool FC welcomed the announcement. Managing director Ian Ayre said: "This is another significant step forward in the campaign for justice for Hillsborough families and survivors. We will follow the progress of this investigation and remain resolute in our support of the families and survivors as they continue with their battle to bring those responsible for the tragedy to justice. Former home secretary David Blunkett, MP for Sheffield Brightside and Hillsborough, said the investigation should not reflect unfairly on all current or former South Yorkshire officers. He said: "It is entirely right that no stone should be left unturned in ensuring that the families of the victims of events 23 years ago can be assured that the truth has been revealed and those who have not been held to account should have to be. I hope that this can be done by cooling the temperature in a way that allows fairness for individuals and a reflection of the many officers in the South Yorkshire force who, on that tragic day, were doing their best in circumstances not of their making and where they themselves were deeply critical of the leadership they were failing to receive. It is critical that the present South Yorkshire force are not pilloried and that the morale of those now serving should be maintained.