Conservative calls for Andrew Mitchell to be returned to government are gathering momentum, after it was suggested last night police officers could have fabricated evidence against him.
The Metropolitan police has begun an investigation following the emergence of CCTV footage which places the police's account of events on the evening of September 19th into doubt.
The footage, shown on Channel 4 News, revealed CCTV footage of the entrance to Downing Street showing Mitchell leaving with his bicycle. He later resigned after an intense media backlash against his rant at the police, in which he allegedly described the on-duty officers as "f***ing plebs".
The CCTV footage appeared to clash with the police's account of events, which suggested he had engaged in a lengthy foul-mouthed rant against the officers on duty.
The leaked police log claimed several members of the public were present, "as is the norm opposite the pedestrian gate". It stated: "As we neared it, Mr MITCHELL said: 'Best you learn your f------ place...you don't run this f------ government...You're f------ plebs."
CCTV footage clearly showed there was only one man taking an interest in the incident outside the Downing Street gates.
Now it has emerged a man a sent an email from home in Ruislip to John Randall, his MP, the deputy chief whip to Mitchell, saying he was present with his nephew. That backed the police log, which claimed "several members of the public looked visibly shocked" by Mitchell's alleged remarks.
Earlier this week David Cameron was told the man who sent the email was a serving police officer, Channel 4 claimed.
Mitchell, speaking to Channel 4, said: "It has certainly shaken my life-long support and confidence in the police and I believe now there should be a full inquiry so that we can get to the bottom of this."
This morning the Met confirmed it would mount a probe immediately.
"The allegation that a serving police officer fabricated evidence is extremely serious," it said in a statement.
"The Met is now conducting a thorough and well-resourced investigation to get to the truth as soon as possible."
Cameron announced in prime minister's questions the Independent Police Complaints Commission would 'supervise' the Met's probe.
A Downing Street spokesperson said: "Any allegations that a serving police officer posed as a member of the public and fabricated evidence against a cabinet minister are exceptionally serious.
"It is therefore essential that the police get to the bottom of this as a matter of urgency."
Labour politicians struggled to balance their desire to see a disgraced minister stay disgraced with the need for the truth to emerge.
Shadow home secretary Yvette Cooper pointed out Mitchell had admitted swearing at the police – and that the Met commissioner was standing by the accounts of those on the gate.
"It is essential that there is a full and independent investigation into what happened in Downing Street as we and others called for three months ago," she said.
"The prime minister was urged repeatedly to set up a proper investigation to get to the facts and refused to do so, and it is incredible that three months on we still don't have clarity about what happened.
"Given the seriousness of this issue and the importance of trust between the police and government ministers, this must not be allowed to drag on any longer."
The call for an independent probe, rather than the internal one now being undertaken by the Met, was echoed by home affairs committee chair Keith Vaz.
Writing to Hogan-Howe, Vaz urged: "Given the level of public interest, the place where the incident occurred and the issue of police integrity there is clearly a need for a robust, transparent and comprehensive investigation."
David Davis called on Met commissioner Bernard Hogan-Howe to establish the motivation of the police officers involved.
He told the Today programme: "This is a shocking revelation that a senior police officer seems to have masqueraded as a civilian, and acted in a way which effectively completely undermined Andrew Mitchell in the eyes of the prime minister and Downing Street right at the point they were making the decision of whether we support him or not."
Former Conservative party leader Michael Howard told the same programme he was "appalled" by the allegations and called for Mitchell to be restored to government "at the earliest opportunity".
Speculation is now rife that Mitchell will be seeking a return to public life beyond his current role as a backbench MP. It seems unlikely he would be restored to his old job as chief whip, prompting suggestions he may be in line for an international job.