Police officers to be interviewed as Scotland Yard ramps up inquiry into possible wider criminal conspiracy to target Andrew Mitchell

Met investigating possible conspiracy to target Chief Whip after email revelations cast doubt on integrity of officers

Mitchell admits swearing but denies using the term 'pleb' (Getty Images)

Two police officers who claimed Andrew Mitchell called them a “pleb” in a row at the gates of Downing Street are to be interviewed as Scotland Yard ramps up its inquiry into a possible criminal conspiracy to target the former Chief Whip.

Thirty officers are investigating various angles, including whether another officer who claimed to have witnessed the row while off-duty was the source of a leak to two newspapers that sparked the furore and led to Mr Mitchell’s resignation.

Amid demands for Mr Mitchell’s reinstatement to the front bench, David Cameron called yesterday for an inquiry over possible attempts by a police officer to “blacken the name” of a senior minister. Scotland Yard announced a “large-scale and complex” investigation into the confrontation between Mr Mitchell and two diplomatic protection officers.

It follows doubts raised over police integrity following the release of CCTV footage that questioned the accuracy of the police log leaked to newspapers and emails allegedly sent by a third diplomatic protection officer to Mr Mitchell’s deputy that provided corroborating evidence.

The email, obtained by Channel 4, was released yesterday. The writer said Mr Mitchell shouted “YOU PLEBES !!” [sic] and added that he was “totally taken aback by his … behaviour and the gutter language he used.”

Both the email and the leaked police log compiled by one of the two officers claimed several members of the public witnessed and were shocked by the language used by the Chief Whip. Mr Mitchell admits swearing but denies using the term “pleb”.

The officer who sent the email is now facing allegations that he made up that part of the statement after CCTV footage revealed no passers-by lingering at the gate when the argument took place. A diplomatic protection officer was arrested on Saturday and has been suspended from duty.

Last night it also emerged that David Cameron and the Cabinet Secretary Jeremy Heywood were in possession of the CCTV evidence which Mr Mitchell claims backs his version of events. However neither man raised the discrepancy with the Metropolitan Police.

Last night government sources said that while they felt the CCTV images “raised serious questions” over the police account of the incident it was decided to “let it lie” because of the need to maintain a good relationship with the officers guarding senior politicians. Bernard Hogan-Howe, the Metropolitan Police Commissioner, has backed the accounts of the two officers on duty in Downing Street.

“It certainly informed the Prime Minister’s decision that Mr Mitchell should not be required to resign,” said one source. “And while it did raise questions over the police log of the incident a decision was taken not to push it.”

However, as a result of continuing pressure from the media and the Police Federation Mr Mitchell did eventually stand down. When subsequently he requested copies of the CCTV footage under the Data Protection Act this was not opposed by Downing Street.

The police investigation into the affair is likely to cause significant tensions between senior politicians and the men who are paid to keep them safe. The former Tory leader Lord Howard of Lympne, an ally of Mr Mitchell, said he was “appalled” that a police officer could have fabricated evidence while the former Conservative shadow Home Secretary David Davis said Mr Mitchell had been the victim of “a serious injustice”.

“This is a shocking revelation,” he said. “A police officer masqueraded as a civilian and acted in a way which completely undermined Mr Mitchell in the eyes of Downing Street right at the point they were making the decision: do we support him or not?”