DAVID Cameron went into the first full day of campaigning for the May 7 general election buoyed by an instant poll suggesting he edged victory over Ed Miliband by a margin of 54 to 46 per cent in the live TV clash.

But the Labour leader's supporters insisted his performance on the Battle for Number 10 programme showed why the Prime Minister was unwilling to face him in a head-to-head TV debate.

They pointed to details in the ICM poll for The Guardian which suggested that wavering voters were more likely to have moved towards Labour than the Tories.

Although the two leaders were in the same studio for the 90-minute Sky News/Channel 4 show, they did not share a stage as they took questions from veteran TV inquisitor Jeremy Paxman and a studio audience.

Both took the opportunity to spell out core election messages - Mr Cameron promising to deliver a "strong economy", while his Labour rival insisted: "We can do a lot better than this. We're a great country." But there was little in the way of new policy and no killer blows dealt.

Mr Cameron was faced with questions about his friend Jeremy Clarkson - saying the BBC's decision to sack him was "absolutely right for them" - and admitted that he would not be able to live on the kind of exclusive zero-hours contract that the coalition has outlawed.

Mr Miliband told a studio audience his relationship with brother David was still "healing" after their bruising battle for the Labour leadership, but said he still thought he was the right man for the job.

And he dismissed suggestions that he was a "north London geek" without the steel needed to lead the country, insisting: "Am I tough enough? Hell, yes, I'm tough enough."

Mr Miliband even won plaudits from Ukip leader Nigel Farage, who said he had won the personality battle. But his claim to have stood up to Rupert Murdoch prompted a withering response from the News Corp boss, who tweeted: "Thanks for two mentions, Ed Miliband. Only met once for all of 2 minutes when you embarrassed me with over the top flattery."

Mr Cameron said the UK was "immeasurably stronger" after five years of his premiership and claimed that "we've turned the economy round".

He defended his stewardship of the NHS, after an audience member accused him of breaking his promise not to impose a top-down reorganisation, telling her he had increased spending on health by £12.7 billion and recruited thousands of doctors and nurses while removing swathes of managers.

The Conservative leader told his audience in the studio and at home watching TV: "You are going to have to make this huge choice in 42 days' time. What I have learnt in the last five years is that nothing you want to do will work without a strong and growing economy.

"The schools we want for our children, the hospitals we want when we are ill. These things need that strong economy."

Mr Miliband said: "I think this is a choice between those who think this is as good as it gets for Britain and those who think we can do a lot better than this.

"The Prime Minister said he couldn't live on a zero hours contract, well I couldn't either, so let's do something about it."

Mr Cameron defended his decision to announce that he would not seek a third term if re-elected in May. He said he was "passionate about having another term" and insisted he would serve "every day" of it but would not be "one of those leaders like Chairman Mao who thinks you can go on and on and on".

Mr Paxman told the PM that many voters found it "problematic" that he had chosen to surround himself with people like Clarkson, ex-HSBC boss Lord Green and former News of the World editor Andy Coulson, asking: "What do you have in common with all these rich people?"

But the PM defended his links with Clarkson and Green and said: "The aspersion you are trying to cast is completely ridiculous."

The interviewer told Mr Miliband that even Labour MPs considered him a "liability" and that he was seen as "a north London geek" by many voters, who thought "what a shame it's not his brother".

But the Labour leader insisted the brickbats were "water off a duck's back", adding: "People have to decide - do they want my ideas, do they want my principles when I stood up not just to President Obama, but Rupert Murdoch, the energy companies, the banks?

"I don't care what the newspapers write about me, because what I care about is what happens to the British people."

He said he was "a pretty resilient guy" who had been "underestimated at every turn", telling Mr Paxman: "I know I'm the right man for the job - that's why I'm sitting here and that's why I believe that I'm the best choice to be Prime Minister."

When Mr Paxman questioned the Labour leader's insistence he would not get into a "bargaining game" with the Scottish National Party in a hung parliament, Mr Miliband quipped: "Don't be so presumptuous, there's six weeks to go - you don't get to decide the election result. You're important Jeremy, but not that important."