Justice Secretary Dominic Raab has told Sky News he would resign from the cabinet if bullying claims against him are upheld.
The deputy prime minister is being investigated by senior lawyer Adam Tolley KC over a string of formal complaints by civil servants about his conduct.
Speaking to the Sophy Ridge On Sunday programme, Mr Raab restated he had “behaved professionally throughout” and pointed out he had called for an inquiry himself when the accusations were first made.
Asked whether he would quit if a complaint was upheld, the cabinet minister initially refused to be drawn and said he was “not going to start speculating on what the outcome might be” and that it was a “hypothetical question”.
But when pressed further, he said: “Look, if an allegation of bullying is upheld, I will resign.”
Mr Raab also dismissed calls for him to stand aside while the investigation is carried out and argued it was “ultimately for the prime minister to decide”.
He added: “But I think actually just by lodging complaints you can knock out a cabinet minister or a senior figure, I’m not sure that’s right.
“We believe in innocent until proven guilty in this country and look, I’ll cooperate fully with the inquiry and I’ll respect the outcome of that.”
He went on: “If you believe in innocent until proven guilty, you wouldn’t want to penalise people until you have got the outcome and I can see why that would politicise the process of lodging complaints because you can effectively, for months on end, remove cabinet members or other leading political figures.”
Speaking to the BBC later, Mr Raab again defended his behaviour but said he had learned lessons from his dealings with civil servants.
He said: “I think the lion’s share of the time, the vast majority of cases and the time we spend together, civil servants and ministers work very effectively together.”
Read more: The five days of allegations against the deputy PM
On whether there should be “more plain speaking in politics”, he said: “Yes, absolutely.
“What we need, and I think this can be reconciled absolutely with having a zero tolerance on bullying, you need ministers who come in and correctly but directly challenge assumptions, test ideas – that is the way we get the best out of government.”
But Dave Penman, general secretary of the public services union, the FDA, told the BBC civil servants “don’t have the confidence” to challenge bullying or harassment by senior figures in Whitehall.