Shadow chancellor John McDonnell has denied Labour is preparing to lose a pair of crunch by-elections next month, but insisted the results cannot be judged on past performance.

Defeats for Labour in Stoke-on-Trent Central and Copeland on February 23 would be unprecedented in the history of by-elections, which almost never see Opposition parties lose seats during a Government's term in office.

But Ukip leader Paul Nuttall's decision to stand in Stoke, which he described as "the capital of Brexit", indicates his belief that he can make good on his promise to replace Labour as the party of the working class in the Midlands and north of England.

There are also concerns over Copeland, where the Tories have narrowed the gap in recent years.

Mr McDonnell's insistence that the shake-up of British politics caused by Brexit means Labour cannot be judged on past performance could spark concerns in the party.

But he said he thinks Labour will win both polls.

The shadow chancellor told BBC One's Andrew Marr Show: "Since Brexit you can't calculate by-election results on what's gone on in the past so what we're going to do is fight for every vote, and that's what we're going to do.

"I'm angry by the statements by Mr Nuttall today, that's taking Stoke for granted - he's basically saying he's going to win it.

"You don't take the election for granted."

Asked if he was preparing to lose, Mr McDonnell replied: "Not at all, we're preparing to fight this vote by vote and I think we're going to win because we'll have strong local candidates campaigning, yes on Brexit, but also on the NHS.

"And remember, Paul Nuttall wants to privatise the NHS, I think people will wake up to those threats and as a result I think we will win."

Speaking on ITV's Peston on Sunday, Mr Nuttall said that Ukip would never run on a platform of privatising the NHS.

The Ukip leader added he believed the party would come "very close" to winning in Stoke, as it prepared to embark on its most professional election campaign ever.

He said: "We now have a Labour party that I feel, and many working class people feel, has stopped representing not only their grassroot members, but also their voters.

"You have a Labour party which is more at home talking about the issues that swirl around the Islington dinner party, such as Palestine, climate change and fair trade, and not really focusing on the issues that matter to working class people."