The behaviour of some police officers in the Plebgate scandal fell below acceptable standards but there are questions over how serious their wrongdoing was, Sir Hugh Orde has said.
The head of the Association of Chief Police Officers (Acpo) also criticised the Independent Police Complaints Commission's handling of the affair and urged the creation of a new police ombudsman.
Orde appeared to back the decision of three forces not to discipline officers who have been accused of stitching up Andrew Mitchell and costing him his cabinet post. He spoke as the policing minister Damian Green in a speech on Wednesday said the "corrupt behaviour" of a small minority of police officers could have a "corrosive effect on the reputation" of them all and undermined justice.
A police-led investigation into the conduct of the three officers concluded they made misleading statements about a meeting with Mitchell in October last year to discuss the Plebgate affair. They accused him of refusing to elaborate on what happened during an altercation at the gates of Downing Street a month earlier with two diplomatic protection officers from the Metropolitan police and said his position was untenable.
A recording of the meeting revealed Mitchell gave them his word he had not called police officers in Downing Street "fucking plebs" during the altercation as he tried to ride his bike through the gates.
But the IPCC challenged the findings of the investigation which they supervised questioned the "honesty and integrity" of the three officers at the meeting and called for them to be disciplined. Theresa May, the home secretary, said Mitchell deserved an apology.
Speaking to BBC Radio 4's Today programme, Orde said the chiefs of West Mercia, West Midlands and Warwickshire, whose forces were represented at the meeting, deserved a chance to put their case across for not disciplining the officers at a hearing of MPs. All three chief constables were backed by their police and crime commissioners on Wednesday.
"I think what's important is the service is seen to be transparent and recognise where we get things wrong. We have a history of doing that and being prepared to explain in the public forum why we made the decisions we made," he said.
"It seems to me in this case there's no issue that the finding by the police service was the officers' behaviour fell below the standard, the question is the quantum of seriousness and I think that's why the [West Mercia] chief constable is determined to explain that the full investigation to the home affairs select committee and be held to account and judged on that."
In a speech to the College of Policing on Wednesday, Green added his voice to the growing row between politicians and police leaders and rank and file.
"Whilst I can say that corruption and misconduct in the police are thankfully the rare exception and not the norm, where it does occur - that is in the small minority of officers whose behaviour is entirely unacceptable - it can have a corrosive effect on the reputation of all police officers, undermines justice and fundamentally strikes at the heart of public confidence in the police," he said.
Orde, addressing the wider issue of how complaints against the police are investigated, said the IPCC should have investigated the officers' conduct earlier and called for a new police ombudsman.
Acpo later clarified Orde's comments, saying he was simply raising a matter for public debate when he said a new ombudsman to investigate complaints could be created.
A spokesman said Orde's suggestion of a police ombudsman could actually mean reform of the IPCC, an extension of the IPCC's powers or a separate ombudsman.
The IPCC decided to supervise the investigation into the officers' conduct, leaving it with less power to direct the conclusions. When the West Mercia inquiry concluded that the officers made ambiguous and misleading public statements about the meeting but did not deliberately lie, the IPCC went public to say it disagreed and the officers should be disciplined. But it admitted it was powerless to force disciplinary action to be held as it had only supervised the investigation.
"It is a matter of record that this was a case which the service tried to have independently investigated by the IPCC, who made a decision that it should be investigated by the service," he said.
"I think the current decision by the home secretary to take money from the service to support the IPCC, maybe that would be better spent looking at the bigger picture and [ask] do we need a police ombudsman system in the rest of the UK."
"When I took over service in Northern Ireland the key success factors for me was I had a completely independent policing board to hold me to account, we now have PCCs in this country who hold police to account, I had a police ombudsman who would investigate every complaint from the public independently of me. I had absolute confidence in that system as did the public. I think it's a very good model, it is of course a very expensive model, so we have to ask some hard questions about how important this is, I see it as very important."
His comments came as Jack Straw, a former home secretary, said the Police Federation showed a "poverty of leadership" during the affair.
"[Officers had] the idea that if they embroidered the truth, and I put that mildly, then they could get the scalp of a Conservative cabinet minister of an administration with whom they were in conflict at the time.
"Now, what this shows, I think, is a poverty of leadership by the federation and a readiness by them to resort to completely inappropriate behaviour, which you would not expect of anybody but least of all of police officers."