Labour's Jeremy Corbyn and Tory leader Theresa May had a tough interrogation from Question Time audience members in an election special.
Mrs May faced nurses angry over a pay cap and a woman who had suffered ill treatment in a work assessment.
Mr Corbyn was repeatedly asked if he would fire nuclear weapons if Britain was under attack, after ruling out "first use" of them.
He said it was a "shame" Mrs May had refused to debate him "head-to-head".
The two leaders were questioned consecutively in the 90-minute special on BBC One.
During her 45-minute grilling, Mrs May repeated her mantra that "the only poll that matters is the one that takes place on polling day" and insisted she was right to have the "balls" to go to the country.
In a swipe at the prospect of Labour running the country, she said: "We have a situation at the moment where if Jeremy Corbyn was to get into Number 10, he'd be being propped up by the Liberal Democrats and the Scottish nationalists.
"You would have Diane Abbott, who can't add up, sitting around the Cabinet table, John McDonnell, who is a Marxist, Nicola Sturgeon, who wants to break our country up, and Tim Farron, who wants to take us back into the EU - the direct opposite of what the British people want."
Mr Corbyn began by saying there would be "no deals" with other parties and condemning Donald Trump's ditching of the Paris climate agreement.
The Labour leader said: "I'm very sorry this is not a debate, this is a series of questions. I think it's a shame the prime minister hasn't taken part in a debate."
He insisted that his party's manifesto was not just a "wish list," saying it was "time to invest in our country".
He was challenged about his approach to Brexit and said the UK would not "necessarily" be poorer as a result of leaving the European Union.
Analysis by BBC Political Editor Laura Kuenssberg
After a bumpy few days, Theresa May seemed to be more on the front foot this evening, trying to reassert her authority over her campaign.
In contrast, Jeremy Corbyn who had been lapping up the political attention, and setting much of the momentum, seemed almost irritated by the end.
Yet in truth, tonight saw neither of the rivals drop a dramatic clanger, nor neither of them turn out a surprisingly stellar performance.
On Brexit, Mr Corbyn defended his team's ability to handle the negotiations, with plans for immediate legislation to protect the rights of EU nationals in the UK. He said a government led by him would work to "guarantee trade access to the European markets and protection for the conditions we have achieved through EU membership".
He was repeatedly quizzed about whether he would use nuclear weapons if Britain was under threat, eventually telling one audience member: "I don't want to be responsible for millions of deaths and neither do you."
The Labour leader has made no secret of his opposition to Trident, but has agreed to press ahead with renewal of the system after being defeated in an internal debate on party policy.
He said he would work for a world free of nuclear weapons and "do everything I can to ensure that any threat is actually dealt with earlier on by negotiations and by talks, so that we do adhere to our obligations under the nuclear non-proliferation treaty".
Mr Corbyn was challenged by an audience member over why he had "never regarded the IRA as terrorists".
The Labour leader said: "I have deplored all acts of terrorism by anybody in Northern Ireland or anywhere else."
The Conservative leader faced questions about her previous support for staying in the EU.
"I did say at the time I thought there were advantages to remaining in the European Union," she said, but added that she had not said "the sky would fall in" if Britain left.
But she said she now wanted to "deliver on the will of the people" but also to "make sure we make a success" of Brexit.
She has also hit back at criticism of her decision not to take on Jeremy Corbyn in a head-to-head debate, saying: "I don't think seven politicians arguing among themselves is that interesting or revealing."
She faced detailed scrutiny from the audience on her planned social care reforms, after an audience member asked: "What is the point of us working our whole lives and building up a pension if it's all going to be taken away again to pay for our care should we need it?"
Mrs May insisted the reforms were "fair".
She also came under fire from nurses over their experience of incomes falling in real terms, as a result of the 1% cap on annual public sector pay rises. She said public money had to be "managed carefully".
She used attack lines first tried by Home Secretary Amber Rudd in Wednesday's seven-way debate, accusing her rival parties of having a "magic money tree" and repeatedly attacking the credibility of shadow home secretary Diane Abbott.
One questioner, with mental health issues, was close to tears as she spoke about her experience of a work capability assessment.
Mrs May said she would "make no excuses" for the way the woman had been treated, saying improvements had to be made to the work capability assessments and that people with mental health issues had to be given "more support at an early stage".
She also faced questions about the foreign aid budget, education and Paris climate agreement.
She said: "I have spoken to Donald Trump and told him that the UK believes in the Paris agreement."
Another Question Time special on BBC One on Sunday will see Lib Dem Leader Tim Farron go up against SNP leader Nicola Sturgeon. It will start at 17:55 BST and last an hour.