Prime Minister Boris Johnson said on Saturday he was making a "huge amount of progress" towards a Brexit deal with the EU, in an interview in which he compared Britain to the Incredible Hulk.

"It's going to take a lot of work between now and October 17" when EU leaders gather for their final summit before Britain's scheduled exit from the bloc, he told the Mail on Sunday newspaper.

"But I'm going to go to that summit and I'm going to get a deal, I'm very confident. And if we don't get a deal then we'll come out on October 31."

His comments came ahead of talks with European Commission chief Jean-Claude Juncker and the EU's chief Brexit negotiator, Michel Barnier, in Luxembourg on Monday.

In an odd analogy, Johnson compared Britain to the comic book character Hulk.

"The madder Hulk gets, the stronger Hulk gets and he always escaped, no matter how tightly bound in he seemed to be — and that is the case for this country," he said.

"We will come out on October 31 and we will get it done, believe me."

But the extent of the parliamentary opposition to Johnson's approach was laid bare on Saturday when one of his Conservative MPs defected to the pro-European Liberal Democrats.

Former universities minister Sam Gyimah has strongly criticised Johnson's threat to leave the EU with no deal, and has called for a re-run of the 2016 Brexit referendum.

'Progress'

Johnson took office in July promising to leave the EU next month with or without a deal, but has faced resistance from the House of Commons.

Rebel Conservatives joined opposition MPs last week to rush through a law to delay Brexit until January if he does not get a deal in time.

Johnson wants to renegotiate the terms struck by his predecessor, Theresa May, which were rejected by parliament — but EU leaders insist the deal is the best on offer.

The main sticking point is the so-called backstop plan to keep open Britain's border with Ireland, which could keep Britain tied to EU trade rules long after Brexit.

"When I got this job everybody was saying there can be absolutely no change to the withdrawal agreement," Johnson said.

"They have already moved off that and, as you know, there's a very, very good conversation going on about how to address the issues of the Northern Irish border.

"A huge amount of progress is being made."

However, Downing Street has downplayed any major breakthrough in Monday's talks.

Johnson repeated that "under no circumstances" would he delay Brexit.

'Stark choice'

Twenty-one Conservative MPs defied Johnson to back the legislation blocking a "no deal" Brexit, and were swiftly expelled from the governing party.

One of them was Gyimah, who now becomes the Liberal Democrats' 18th MP in the 650-seat House of Commons.

The 43-year-old was once viewed as a rising star in the Conservatives and briefly ran against Johnson for the party leadership.

But he said Saturday: "Boris Johnson created a stark choice for moderate, progressive MPs in the Conservative party -- to accept a no deal Brexit or walk away from public life.

"I choose to continue to fight for the values I have always believed in, as a Liberal Democrat."

His defection is the sixth to the Lib Dems this year, and comes just days after a similar move by Conservative MP Phillip Lee.