Cameron regains high ground as Brown struggles in fiercest debate yet - VIDEO

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In the most confrontational of the three debates, the Tory leader emerged as the clear winner from instant polls just seven days ahead of the general election giving fresh momentum to his campaign.

Following Gordon Brown's clash with pensioner Gillian Duffy on Wednesday when he called her "bigoted" after she raised concerns over immigration, the three party leaders clashed fiercely over the issue.

Mr Brown referred to the incident in his opening statement – admitting "there is a lot to this job and, as you saw yesterday, I don't get all of it right" – but it was Liberal Democrat leader Mr Clegg who came under most pressure over his proposed "amnesty" for illegal immigrants.

The Tory leader said it was "profoundly misguided" and the Prime Minister said it was sending out the "worst possible message", as Mr Clegg pleaded with the other men to "get real" over the problems of immigration.

The three also traded blows over tax proposals, spending cuts, banking, and the euro. Mr Cameron came under most pressure for his proposal to increase the inheritance tax threshold, which his opponents portrayed as benefiting millionaires, while Mr Brown was repeatedly attacked over Labour's handling of the economy and their record in office.

In the wake of this week's accusation that voters were being kept in the dark on post-election tax and spending cuts, the three men were urged to provide honesty over their cuts but gave no new detail on their proposals.

Instant polls suggested Mr Cameron was the clear winner. YouGov put the Tory leader of 41 per cent, well ahead of Mr Clegg on 32 per cent and Mr Brown on 25 per cent, while ComRes found the verdict was closer with Mr Cameron on 35 per cent and Mr Clegg on 33 per cent and Mr Brown on 26 per cent.

In their closing pitches to millions of viewers, Mr Cameron urged voters to go for a "clean break" next week, warning there would be "more of the same" under Labour or "uncertainty" with the Liberal Democrats.

"I believe the test of a good and strong society is how we look after the most vulnerable, the most frail and the poorest," he said.

"That's true in good times but it's even more true in difficult times. And there will be difficult decisions but I want to lead us through those to better times ahead.

"I think I've got a great team behind me, I think that we can do great things in this country."

With his party having soared in the opinion polls since the first debate a fortnight ago, beating Labour into third place in some of them, Mr Clegg told voters not to be frightened off by the two other parties.

"Don't let anyone scare you from following your instincts," he said at the end of another assured performance. "Together next week we can change Britain for good."

Echoing Mr Cameron's optimistic note, he insisted the country could do "so much better" than broken promises by the other parties and said he would work "tirelessly" to deliver greater fairness.

"If you believe like I do that we can do things differently this time, then together we will really change Britain. Don't let anyone tell you it can't happen. It can."

Meanwhile Mr Brown, who sought to appeal to Labour's core votes with jibes at "same old Conservative party", was left to urge voters to stick with more of the same as he insisted, "I do know how to run the economy in good times and bad".

The Prime Minister admitted that if there was no shift in the polls between now and May 6 the Conservatives could be in office, perhaps in coalition with the Liberal Democrats.

"This would put the economy in jeopardy," he said. "Things are too important to be left to the risky policies of these two parties. They are not ready for Government."

Last night's debate was the third over the past three weeks which have transformed the election campaign. The first dealt with domestic policy and propelled Liberal Democrat leader Nick Clegg into the national spotlight, leading to the possibility of a hung parliament.