The Debate: Seven Leaders, Seven Key Moments

After seven party leaders vied for attention from undecided voters in the studio audience and at home, Sky News looks at seven key clashes between the politicians.

Nigel Farage vs Leanne Wood: Health Tourism

Many leaders spoke out against the privatisation of the NHS during their opening statements. But Nigel Farage decided to grasp another nettle: health tourism.

In the free-flowing debate, he claimed that 7,000 people are diagnosed as HIV positive every year - but 60% of them are not British nationals.

"You can come into Britain, from anywhere in the world, get diagnosed with HIV and get the retro-viral drugs which cost up to £25,000 per year, per patient. We need to put the National Health Service there for British people and families," the UKIP leader said.

Leanne Wood, from Plaid Cymru, was the first to reply to Mr Farage's point – and battled through his interruptions to secure the first round of applause of the evening.

"This kind of scaremongering rhetoric is dangerous. It divides communities and creates a stigma to people who are ill. I think you should be ashamed of yourself," she replied.

Nick Clegg vs Ed Miliband: The Economic Crash

Another barbed exchange was between Nick Clegg and Ed Miliband, after the Labour leader took the Deputy Prime Minister to task over his U-turn on tuition fees back in 2010.

"It was a broken promise, you betrayed the young people of our country," he said.

Mr Clegg described his rival's stance as "pious", shooting back: "This is the man who was part of a government that said 'no boom and bust in the economy' and crashed our economy - jeopardising the future generations and life chances of millions of people.

"I've apologised, I've taken responsibility for the mistakes I've made. Why don’t you, in the front of the British people, say 'I'm sorry for crashing the British economy?'"

Mr Miliband ducked the question - but brought David Cameron into the row, replying: "The banks were under-regulated, but there was a global financial crisis. David, as leader of the opposition, you were saying banks were over-regulated, so I'm not going to take any lectures from you on the global financial crisis."

Both received applause.

Leanne Wood: "I Agree With Nicola"

One of the biggest buzz-phrases which emerged during the last general election in 2010 was "I agree with Nick", as Gordon Brown extended a friendly hand towards the Liberal Democrats - kingmakers during the first hung parliament in decades.

Five years on, and Leanne Wood of Plaid Cymru had slightly adapted the phrase to "I agree with Nicola", as she aligned her party with the SNP on several major issues.

Nicola Sturgeon vs Cameron, Miliband and Clegg: The EU

The SNP leader certainly made things interesting when she launched a challenge to three parties at once - asking them to make a pledge to the four countries that comprise the United Kingdom ahead of any in-out referendum on the EU.

She said: "Nigel Farage wants to take the UK out of Europe - and David Cameron is taking us dangerously close to the exit door.

"They spent a lot of time talking about the UK family of nations during the Scottish referendum, but will they give a commitment that if there is an in-out referendum, no one part of that family of nations will be taken out of Europe against its will?

"Will the vote be counted separately in each of the four nations so none of us can be dragged out?"

David Cameron vs The Heckler: Homeless Veterans

The Prime Minister was praising the "brave and professional" armed services around the world when he was interrupted by a heckler from the audience.

Victoria Prosser made an intervention and shouted about how many homeless veterans were on the streets after completing their service.

Mr Cameron replied: "The lady makes an important point. There are people coming out of the armed services who have difficulties, and we should put money into armed forces charities helping homeless people."

After the debates, Ms Prosser explained: "He is using their name to garner votes because it might be a vote winner."

Nick Clegg vs Nigel Farage: Foreigners

During the segment on immigration, UKIP's leader claimed that, at 300,000, net migration now is 10 times higher than it was during World War II.

Mr Clegg decided to take Mr Farage to task, saying: "I'm married to a foreigner, you're married to a foreigner. Let's be open-hearted and generous-spirited."

Earlier, Nicola Sturgeon had said: "There isn't anything Nigel Farage won't blame on foreigners."

David Cameron vs Ed Miliband: Jobs

Towards the end of the debate, Ed Miliband returned to one of his pet subjects: zero-hours contracts, and claimed the Conservatives' "trickle down" economic experiment had failed.

Mr Cameron simply said: "Never mind zero-hours; with Ed there'd be zero jobs."