Prime Minister David Cameron urged three police officers caught up in the so-called Plebgate row to apologise for their actions when they appear before MPs today to answer questions about their meeting with former Cabinet minister Andrew Mitchell.
Following the meeting last October, Police Federation representatives Inspector Ken MacKaill, Detective Sergeant Stuart Hinton and Sergeant Chris Jones said that the then-Conservative chief whip had failed to give an account of his altercation with officers at the gates of Downing Street.
The officers, who were representing the forces of West Mercia, Warwickshire and West Midlands, were later accused of trying to discredit Mr Mitchell, but were spared misconduct proceedings by an internal investigation.
But the Independent Police Complaints Commission (IPCC) disputed the findings of the investigation and said there were issues of ''honesty and integrity'' among the three men .
The federation representatives will give evidence to the Home Affairs Select Committee before the chief constables from all three forces - Andy Parker of Warwickshire Police, David Shaw of West Mercia Police and Chris Sims of West Midlands Police - also appear.
Speaking at Prime Minister's Questions in the Commons shortly before the committee hearing, Mr Cameron told MPs: "The former chief whip gave a full explanation of what happened. The police in that meeting said he gave no explanation.
"It is now clear, reading the IPCC report, that the police do need to make an apology. The officers concerned and the chief constables are coming to the House today. I hope they will give a full account and a proper apology to the Home Affairs Select Committee."
Asked whether Labour leader Ed Miliband should also apologise for comments made in the wake of the "Plebgate" affair - when he said Mr Mitchell was "toast" - Mr Cameron said: "It is I think a moment for all of us to consider what we said at the time, and I hope the leader of the opposition will do the same thing."
The Home Affairs Committee will also take evidence from Chief Inspector Jerry Reakes-Williams, who led the internal inquiry into the allegations, as well as Dame Anne Owers and Deborah Glass, the chairwoman and deputy chairwoman of the IPCC.
Mr Mitchell met the three officers after he was accused of calling officers guarding Downing Street ''plebs'' in a foul-mouthed rant as he was asked to cycle through a side gate on September 19 last year.
The Tory MP said he wanted to meet with Mr MacKaill, Det Sgt Hinton and Sgt Jones to ''clear the air''.
A transcript shows Mr Mitchell apologised for swearing at the police officers but denied using the word ''plebs'', while in comments made after the meeting Mr MacKaill claimed the former Tory chief whip refused to provide an account of the incident.
West Mercia Police conducted an internal investigation into claims the three officers were trying to discredit Mr Mitchell but concluded there was no case to answer for misconduct or gross misconduct.
However, the IPCC concluded they should have faced a misconduct panel.
The three officers earlier this week apologised for making a public statement after the meeting at Mr Mitchell's Sutton Coldfield constituency office b ut d id not retract the comments made.
The Crown Prosecution Service is considering whether to bring criminal charges following Scotland Yard's £230,000-plus investigation, known as Operation Alice.
Eight people including five police officers arrested under the investigation were re-bailed.