Boris Johnson has accepted Owen Paterson broke lobbying rules and suggested colleagues misled him over there being cross-party support for his botched bid to protect the senior Tory.

The Prime Minister also admitted on Wednesday that he may have been mistaken in believing that the former Cabinet member had not been allowed to fairly appeal against the investigation that found him guilty.

The remarks are a major row-back from when Mr Johnson ordered Conservative MPs to back a review of the disciplinary system to prevent Mr Paterson’s immediate suspension.

Mr Johnson’s bid ultimately failed when opposition parties refused to join a proposed Tory-led panel to rethink the system and Mr Paterson resigned as MP for North Shropshire.

The former Northern Ireland secretary was found to have breached the rules by lobbying ministers and officials on behalf of two companies paying him £100,000 a year.

But he vigorously denied breaking the rules and linked the investigation into his conduct to his wife’s suicide.

Mr Johnson told the Commons Liaison Committee: “I think it was a very sad case but I think there’s no question that he had fallen foul of the rules on paid advocacy as far as I could see from the report.

“The question that people wanted to establish was whether or not given the particularly tragic circumstances he had a fair right to appeal.”

Chris Bryant, the chair of the Standards committee, which approved the investigation into Mr Paterson, told the Prime Minister that Mr Paterson’s appeal was heard “endlessly”.

Mr Johnson said: “In forming the impression that the former member for North Shropshire had not had a fair process I may well have been mistaken.”

The Prime Minister angered some Conservative backbenchers for ordering to support the doomed changes, which would have seen Tory former minister John Whittingdale lead a review of the disciplinary process and review Mr Paterson’s case.

Commons Leader Jacob Rees-Mogg and chief whip Mark Spencer were blamed in part for not recognising the disquiet in the House.

Mr Johnson said he now accepted there was not the cross-party support for the Government-backed proposals as was suggested to Mr Whittingdale.

“I believed that there would be cross party support for the idea…” the Prime Minister said.

“It was put to me by colleagues that people would feel… and indeed I was fortified in this by the reflection that many people would have felt this was a particularly difficult and sad case.

“I’m very willing to accept I was mistaken in that belief.”

He added: “The intention genuinely was not to exonerate anybody, the intention was to see whether there was some way in which, on a cross-party basis, we could improve the system.

“In retrospect it was obviously, obviously mistaken to think we could conflate the two things and do I regret that decision?

“Yes I certainly do.”