Theresa May suffered a bruising TV grilling while being quizzed over a series of embarrassing U-turns and years of failure to hit her immigration targets.

The Prime Minister was branded a “blowhard who collapses at the first sign of gunfire” by interviewer Jeremy Paxman as he took her to task over reversals on taxation, social care and election plans.

She was heckled by the audience over her manifesto and was uncomfortable facing questions over repeated failures to lower net migration to less than 100,000.

Ms May was far stronger when the interview, part of a wider televised programme involving Labour leader Jeremy Corbyn, covered Brexit as she hit home her message that no deal with the EU is “better than a bad deal”.

Mr Corbyn out-performed low expectations of him during the programme, but reignited confusion over Labour’s position on benefits by saying his party would uprate payments, in contradiction to claims by other senior figures that it would be unaffordable.

Ms May was first questioned over her budget U-turn on plans to increase National Insurance contributions for self-employed people, and was forced to admit she had been pushed to backed down.

Paxman responded: “If I was sitting in Brussels and I was looking at you as the person I had to negotiate with, I would think she is a blowhard who collapses at the first sign of gunfire.”

Ms May hit back that she had successfully negotiated in Brussels on matters of justice and home affairs, but her interviewer moved on to her repeated broken pledges not to hold an election.

Paxman: Brussels negotiators will think May's a blowhard who collapses at the first sign of gunfire

The studio audience applauded loudly as Paxman pointed out the Prime Minister and her spokesmen had promised on six occasions that there would be no general election before 2020, with Ms May saying it had been necessary to change her mind as other parties wanted to frustrate Brexit negotiations.

With the Prime Minister putting the discredited promise to lower immigration to the tens of thousands in a Tory manifesto for a third time, Paxman then told her it had been “her job” when Home Secretary to deal with immigration. Ms May replied: “There is no single moment where you take one measure which changes the immigration figures.”

The Prime Minister was laughed at and heckled by some audience members when she said of Labour plans to boost schools funding “we know the figures don’t add up”, with people apparently amused that it was the Conservative plans on social care that had to be rewritten.

Liberal Democrat leader Tim Farron called it a “car crash”, while the SNP’s Nicola Sturgeon tweeted: “It has become painfully clear in last half hour why the PM is dodging leaders’ debates in this election.”

Even some Tory commentators suggested it had not been the strongest performance, such as LBC radio host Iain Dale who said on Twitter: “Let no one pretend that this was comfortable for her. It patently was not.”

It comes as Ms May prepares to give a major speech on Tuesday in which she will try to realign the election on Brexit, a subject she was much stronger on during her TV grilling.

Brexit Secretary David Davis defended his leader after the programme, claiming Ms May gave a “strong, mature, considered performance”.

Jeremy Corbyn defends immigration: The contribution that is made by people who come here is huge

He added: “It couldn’t have been more different to Jeremy Corbyn – who flannelled under pressure and couldn’t get past 30 years of words and deeds that put him on the wrong side of the British people.”

During the show, the Labour leader was quizzed over his apparent support for members of the IRA and for calling members of the Hamas militant group “friends”.

One awkward moment came when he said that his party would uprate benefits – committing his party to a potential £3.6bn spending plan which had not appeared in his party’s manifesto costings.

There was a day of confusion over the party’s approach to the benefits freeze when Labour launched its manifesto earlier this month, with senior figures finally drawing a line under it by admitting it would cost too much to end the lock – due to run until 2020.

But asked by Paxman on Monday if he would freeze benefits, as currently planned by the Conservative Government, Mr Corbyn said: “Benefits will be paid of course. Benefits will be uprated, they will be uprated of course and there will be a higher living wage as I’ve outlined.”

He added: “No, they are not going to be frozen because they will be uprated every year as they should be.”

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During the Sky News/Channel 4 programme, the Labour leader refused to be drawn on whether he would order strikes against a terrorist plotting overseas to attack the UK.

“I would want know the circumstances,” Mr Corbyn said. “You can’t answer a hypothetical question without the evidence. It is a completely hypothetical question.”

After the debate, Labour’s national elections coordinator Andrew Gwynne also dismissed questions on Mr Corbyn’s attitude to the Falklands War after the leader once suggested then-Prime Minister Margaret Thatcher “exploited” it for political gain.