Met police ramp up inquiry into plebgate conspiracy claim Scotland Yard is investigating a possible conspiracy between an officer who claimed to have witnessed the row and others. Scotland Yard has signalled a ramping up of its inquiry into the "plebgate" leak as it announced that 30 officers were working on the investigation. Stung by criticism from Westminster and questions about the integrity of the force, Scotland Yard said it would be following numerous lines of inquiry, including any possible conspiracy between an officer who claimed to have witnessed the row and others. The announcement came as the prime minister was answering questions in the Commons on the row and amid calls for Mitchell to be reinstated in a senior government position. The statement reveals the growing nature of the inquiry. On Tuesday, the Met commissioner, Bernard Hogan-Howe, said the investigation would be over before Christmas, but on Wednesday his force said "the investigation will not be short." Police said in their statement that the investigation by their Department of Professional Standards began after new information was received last Thursday. It will examine who leaked purported details of a clash between Mitchell and police in Downing Street in September. The Metropolitan police investigation will examine if the leak to the media came from officers or, "alternatively, if the source of the leak was via a third party," and "establish who that was and how it was done." The inquiry will also "establish what, if any, criminal or misconduct offences are apparent." The Met added: "There are currently 30 officers progressing the investigation which reflects the serious nature of the allegations and the seriousness with which the MPs view this issue. This is a large scale and complex investigation that has grown to incorporate numerous lines of inquiry. The investigation will not be short. Cameron told MPs at prime minister's questions in the House of Commons: "A police officer posing as a member of the public and sending an email potentially to blacken the name of a cabinet minister is a very serious issue and does need to be seriously investigated. The Metropolitan police service is conducting a thorough and well-resourced investigation to get to the truth of this matter as quickly as possible. The Independent Police Complaints Commission will be supervising the investigation and I think we should allow them to get to the truth. Mitchell was offered strong support by Tory MPs as he listened to prime minister's questions standing at the bar of the Commons. Jeremy Hunt, the health secretary, exchanged what appeared to be friendly words with the former chief whip, who wore a bright pink tie. Mitchell stood next to Greg Knight, a former colleague in the whips' office during the Maastricht rebellions in the 1990s. Knight was brought to the whips' office when Mitchell was appointed chief whip in September. David Davis initially sat in his usual place for the session. But after the Tory MP Rob Wilson asked a question about Mitchell the former shadow home secretary went and stood next to Mitchell. Earlier, Davis, who is leading the campaign to overturn what he called a "gross injustice" against Mitchell, said the published version of a police log of his confrontation with officers in Downing Street would be "torn to shreds" in court. In an escalation of Mitchell's campaign against the police, the former shadow home secretary told the Guardian that the police had been called into question by a series of revelations over the past 48 hours. Labour has called for an urgent inquiry into the incident, saying it threatens trust between the police and ministers. Davis, whose 2005 Tory leadership campaign was run by Mitchell, told the Guardian: The police log has "very similar wording" to two emails sent by a serving officer, who claimed to have witnessed the incident, which were sent to his local MP, John Randall, the deputy chief whip. Randall, who had a strained relationship with Mitchell, handed the emails to No 10 and briefed Mitchell. No 10 says Randall acted properly as a constituency MP. The police officer has now admitted he was not present. The police log and the email claimed the incident was witnessed by several members of the public. CCTV footage of the incident, broadcast on Channel 4 News on Tuesday night, appears to show that only one member of the public stood outside the gate during the incident. The police log claimed that Mitchell made his incendiary remarks that police were behaving like "fucking plebs" as he wheeled his bike to the side gate after being refused permission to wheel it through the main gate. Davis claims that the CCTV footage, which has no sound and does not show their faces at all times, does not show Mitchell speaking to anyone in this precise period. At the same time Downing Street revealed that the second corroborating email, now known to have been sent from a police officer posing as a member of the public who was not present at the scene, had been dismissed as "unreliable" by Sir Jeremy Heywood, the cabinet secretary charged with investigating the incident in the autumn.