Sir Bernard Jenkin said Britain risks being stuck in a perpetual extension of the Brexit deadline if it fails to leave on October 31.
The Conservative MP told talkRADIO’s Julia Hartley-Brewer that another extension would leave the UK “on the run” from the EU.
“The minute you say ‘Oh well, we might extend again’ it means you’re on the run. It means that the EU is going to hunt you down to that deadline and then over that deadline and we’ll finish up extending again,” he said.
“That’s what happened to Theresa May. She finished up on the run from the EU.”
Tory leadership frontrunner Boris Johnson has been criticised by international trade secretary Liam Fox over his Brexit plans.
He said Mr Johnson’s claims that he could use a general agreement on tariffs and trade, known as Article 24, to continue trading with the EU are false.
But Sir Bernard has thrown his support behind the former foreign secretary, telling talkRADIO that Mr Johnson had some “very sensible" Brexit proposals.
Among them are leaving the EU on October 31 with or without a deal.
However, his leadership rival, Jeremy Hunt, has refused to rule out extending the deadline if a deal is in sight.
Conservative MP Alistair Burt, who is supporting Mr Hunt, told talkRADIO the October 31 deadline was “not realistic”.
“Jeremy has made it very clear that he wants to see the United Kingdom leave the EU, but in the best possible circumstances for the United Kingdom,” he said.
“If a deal was possible on November 1, are we to leave on October 31?”.