General election - live: Nigel Farage faces grilling from Andrew Neil after four Brexit Party MEPs defect to Tories

Mr Neil later asks whether it is acceptable to say "Islam is the problem, and until we destroy them the world will never be a safer place".

Mr Farage says: "I have no idea what you're talking about."

When Mr Neil points out that the comment was made by one of his own candidates in Birmingham Ladywood, Mr Farage replies: "Is he? Well I’m not a walking encyclopaedia, sorry.

"I’m sure if some idiot slipped through the net they will have been got rid of immediately."

Mr Farage says that Boris Johnson will win the election on 12 December with a majority and that if he pushes through his Brexit deal in its current form "we will be back in crisis within six months".

Mr Farage says he "couldn't vote" for the deal as it is - but later says "how could I vote for something that isn't Brexit?"

Moving on to the topic of immigration, Mr Neil asks how the Brexit Party leader would fill NHS and social care vacancies if we wants net migration to come down from 212,000 in the past year to 50,000.

Mr Farage's answer is to introduce "work permits". 

"There is a difference, you know, between people coming to work and people coming to settle," he says.

He says the work permits would be on top of the cap of 50,000 and that they would last for "one year, two years".

Mr Neil says: "You would expect someone to come and work in the NHS for just a year? Bring their family?"

Mr Farage says "of course not", to which Mr Neil asks: "But why would they do that?"

The party leader says the number of work permits is a "flexible thing" and agrees there could be 100,000 on top of the 50,000 cap.

"So the 50,000 figure is kind of meaningless isn’t it," says Mr Neil.

Quizzed on whether he would be happy to see the NHS  on the table in a deal, Mr Farage says wealthier people should be encourage to take out private insurance "to life the burden off a system that is struggling to cope".

He adds: "When it comes to opening up the NHS for privatisation, do you want the truth? It’s already happened."

Mr Neil says Mr Farage was heard on the ITV debate defending US president Donald Trump's comments about sexually assaulted women.

"Is there nothing the president can say that would make you disown him," Mr Neil asks.

Mr Farage says: "If we are going to go down this road where any private comment, any man or woman that is distasteful has ever made bars them from public office there’d be no one left."

Mr Neil says the president was "talking about sexually assaulting women and getting away with it".

He asks: "That doesn't deserve to be condemned?"

Mr Farage says he did condemn it, calling it "crass, crude and wrong". He adds: "The argument here being made by the left is that Boris Johnson, because of his flowery articles in The Telegraph, or president Trump, because of these bad comments, should not even be in public life.  I’m arguing we’re going way too far with all of this."

Mr Farage urges voters to "vote tactically", claiming that the Tories would not even be competing in the areas where they are standing if they weren't running Brexit Party candidates.

Mr Neil ends his fourth leaders' interview for the 2019 general election by challenging the prime minister, Boris Johnson, to appear on the programme.

He says: "We have been asking him for weeks now to give us a date, a time, a venue.

"No broadcaster can compel a politician to be interviewed, but leaders' interviews have been a key part of the BBC's prime time election coverage for decades.

"We've always proceeded in good faith that the leaders would participate, and at every election they have - all of them - until this one."

He says he has his interview "oven-ready" for Mr Johnson, adding: “The theme running through our questions is trust. And why, so many times in his career in politics and journalism, critics and sometimes even those close to him have deemed him to be untrustworthy. It is of course relevant to what he is promising us all now.”

Boris Johnson has claimed to lack any knowledge of the overall tax burden rising under Conservative plans, despite party figures predicting such an outcome.

The prime minister said a majority Conservative government wants to deliver a February budget which will cut taxes for working families, and stressed this would be achieved under his plans.

But he said he was "not aware of the data" described when told the manifesto would, overall, raise tax.

A costings document released alongside the party's manifesto shows tax cuts would amount to £3.195 billion in 2020/21 compared to tax increases of £3.32 billion.

The sources of revenue table is also higher in subsequent years compared to the tax cuts figures, with the pledge to maintain corporation tax at 19% the main driver of revenue raising.

PA