David Cameron has praised Andrew Mitchell's "calm and rational" response to the plebgate affair and said allegations that a police officer posing as a member of the public fabricated evidence to damage the former chief whip are "extraordinary".
Speaking during a visit to troops in Afghanistan, the Prime Minister delivered his strongest hint yet that Andrew Mitchell could return to government.
The PM met Mr Mitchell in Number 10 on Monday - the day before Channel 4 News aired the allegations about the serving policeman.
It is understood Mr Cameron believes Mr Mitchell's position has strengthened substantially as a result of the explosive developments.
Meanwhile it has been claimed the former chief whip has "no confidence" in the Metropolitan Police chief Bernard Hogan-Howe.
The Times newspaper said Mr Mitchell's supporters have questioned the impartiality of the Scotland Yard commissioner and are considering involving the Independent Police Complaints Commission (IPCC).
But London Mayor Boris Johnson's official spokesman said the Mayor has "absolute confidence" in Mr Hogan-Howe.
"The Commissioner has assured the Mayor that he is determined to get to the bottom of this as quickly as possible. The Mayor has every confidence in that assurance and knows every avenue will be explored in full."
Police have arrested and questioned two people in the investigation.
A 23-year-old, who is not a police officer or member of police staff, was detained on suspicion of intentionally encouraging or assisting the commission of an indictable offence on December 14.
That date was a day before a member of the diplomatic protection group was arrested on suspicion of misconduct in public office.
The officer is said to have emailed his local MP, Tory deputy chief whip John Randall, posing as a member of the public and accusing Mr Mitchell of calling police "plebs".
The Met has widened the investigation amid growing tensions with senior Conservatives over the treatment of Mr Mitchell, who resigned in October after a month of huge pressure after being accused of calling officers "plebs".
Mr Cameron was asked in interviews if Mr Mitchell could make a comeback.
"One step at a time. Let's get to the truth about what happened," he said. "But I think it has been an extraordinary development, frankly, to find a police officer apparently posing as a member of the public, pretending to have been outside Downing Street at the time and then trying to blacken the name of a Cabinet minister."
Mr Cameron defended Cabinet Secretary Sir Jeremy Heywood over his handling of an investigation into the incident.
The Prime Minister said he took "full responsibility" for the investigation.
He also stressed that the email sent to Mr Randall had not swayed his view at the time that the chief whip did not need to resign.
"We knew this email was unreliable so it did not influence my judgment as to whether Andrew Mitchell should stay in government," he added.
Mr Cameron said that when Mr Randall confronted the individual who allegedly wrote the email, he "flatly denied" being a police officer.