Election 2015: How Cameron, Clegg and Miliband dealt with Question Time quiz

David Cameron certainly looked "pumped up", as he likes to describe it, for this critical chance for the three leaders to try to win over wavering voters.

It didn't start well when he appeared to mishear the opening question on whether he would put to bed rumours that the Conservatives would make big cuts to child benefit.

"No, I don't want to do that," he replied.

He went on to say that he rejected the suggestions of limiting and means-testing child benefit when they were proposed and would do so again.

The most telling follow-up question was from a member of the audience who asked Mr Cameron why he had not explained how he would find the £12bn of savings from the welfare budget.

He wanted to know whether Mr Cameron did not know where the cuts would fall or whether he did know and was deceiving the public.

"How could I possibly vote for you on that basis?" he said.

It was a question pressed home by others in the audience.

Mr Cameron said that over the past five years the government has saved £20bn and needed to find about half that amount in the next parliament.

Trust

He insisted it was right to carry on reforming welfare, but he did not say which benefits would be cut, and though he stressed the importance of child benefit, he did not rule out further limits on who receives it.

The question of trust was an important theme.

When the Tory leader was asked why anyone should trust him on the NHS he turned to his own personal story, talking about the "fantastic care, support and love" he'd received when his disabled son Ivan was ill.

He said the NHS had always been there for his families and would always make sure it was there for others. The prime minister also went back to his key argument on the economy, arguing that you can only have a strong NHS if you have a strong economy.

On stage he brandished the note left behind by a Treasury minister from the last Labour government saying "there is no money left" to press home one of his favourite themes throughout this campaign, that the economy would be at risk if Labour came to power.

Mr Cameron has always avoided answering questions about what he would do if he fails to win an overall majority.

He insisted he was still fighting for a Conservative majority government.

But he did for the first time set out one of his "red lines" if he does need to form a coalition, the pledge to hold a referendum on Britain's membership of the European Union.

He said: "I would not lead a government which did not contain that pledge."

'Deadly serious'

The issue of trust ran through the questions to the Labour leader Ed Miliband, who was tackled over the record of the last Labour government.

Mr Miliband said Labour had got it wrong on bank regulation but had learned its lessons.

He said he was "deadly serious" about reducing the deficit and would do so in a balanced way.

That note saying there was no money left at the end of the last Labour government was raised again, when a member of the audience asked why she should trust a politician who thought such a note was a joke.

Mr Miliband insisted he would get the deficit down and insisted he would do so without cutting benefits.

On this, he did give the categorical assurance Mr Cameron did not give.

The Labour leader gave what he said was a guarantee that he would not cut tax credits, would not cut child benefit or means test it.

He said: "Child benefit and tax credits are on the ballot paper at this election."

Mr Miliband also gave his strongest rejection yet of the Conservative claim that he would have to do a deal with the SNP to get into power, ruling out a coalition or a looser arrangement.

"We are not going to do a deal with SNP," he said, and added "if it means not being in government then so be it".

'No easy promises'

And added that he would not give in to SNP demands on issues such as the Trident nuclear system.

Mr Miliband will be hoping those direct answers will pay dividends with voters, though some in the Question Time audience were unhappy with his opposition to an EU referendum and refusal to set a limit on immigration.

His answer? "I'm not the guy who's going to make the easy promises."

Trust was the big theme of the questions to Nick Clegg too.

The opening question was on how he could be trusted given his broken promise on tuition fees. It's a question the Liberal Democrat leader has faced on many occasions.

He had said sorry and had got it wrong, he told the audience.

Mr Clegg said that given the lack of money when the coalition took power, he'd got "the fairest deal he could achieve in the circumstances".

Mr Clegg sought to turn the question of trust back onto his rivals, saying neither David Cameron nor Ed Miliband would come clean on the compromises they would have to make to win power.

Mr Clegg was very straight on one thing: "I'm not pretending I am going to be prime minister".

He said the Liberal Democrats should be part of the next government to prevent what he called "a lurch to either the right or the left".

All three leaders were tested by the audience, above all on the question of why the voters should trust them.

What we heard was the strongest rejection yet from Ed Miliband on a deal with the SNP and the the strongest commitment yet from David Cameron to an EU referendum.

All three at times looked under pressure under the heat of the television lights but there were no huge mistakes.

The programme did give the wider audience an important chance to compare their performance and policies, just a week before they go to the polling booths.

* Subscribe to the BBC Election 2015 newsletter to get a round-up of the day's campaign news sent to your inbox every weekday afternoon.