Tory leadership contender Jeremy Hunt has refused to guarantee that the UK will leave the EU before Christmas, but said he “expects” it to happen by then.
He would not say when Brexit would take place if he became PM, telling the BBC: “I’m being honest with people”.
Rival Boris Johnson said the UK would leave by 31 October “come what may”.
He also said his remarks on the UK ambassador in Washington, who quit this week over leaked criticisms of Donald Trump, had been “misrepresented”.
Mr Johnson added he did not accept that his failure to support Sir Kim Darroch during a debate on ITV earlier this week had prompted him to resign.
Up to 160,000 Conservative Party members are voting for their next party leader – and UK prime minister – to replace Theresa May.
The BBC’s Andrew Neil has interviewed both contenders for a programme to be broadcast on BBC One at 19:00 BST.
Mr Johnson, a former foreign secretary and mayor of London, is seen as the frontrunner in the contest, and Mr Hunt said his “worry” was that Conservative members would “vote with their hearts instead of their heads”.
He added that the “quickest way” to leave the EU was “to send to Brussels a prime minister who can negotiate a deal that will get through Parliament – and I’m that person”.
Media playback is unsupported on your device
Media captionTory leadership: Jeremy Hunt on making Brexit promises
Foreign Secretary Mr Hunt, who set up his own business before entering politics, was challenged on whether he had the skills to negotiate effectively with the EU.
He replied that being an entrepreneur had given him the “basics”, adding: “In government those same skills I used to negotiate very complex things – like the licence fee deal with the BBC, the NHS pay awards, the protracted dispute to try and get a peace process going in Yemen – that business of negotiation is something I have been doing all my life.”
Mrs May’s Brexit deal with the EU has been rejected three times by MPs, and Mr Hunt said his plan was to remove the Irish backstop – which aims to avoid a hard border on the island of Ireland – from the agreement.
- What’s Jeremy Hunt’s track record?
- And how does Boris Johnson’s record compare?
- Do the people choosing the next PM think like you?
When pushed on what else he would alter, Mr Hunt said that “there may be other elements”,