Tv debate
ITV News presenter Julie Etchingham will moderate the live debateGetty

The leaders of all seven of Britain's major political parties are gearing up to take part in a live televised debate expected to be watched by millions.

The debate between leaders of the Conservatives, Labour, Lib Dems, Ukip, Greens, SNP and Plaid Cymru will be the second televised political discussion of this year's campaign, following March's Q+A session between Ed Miliband and David Cameron.

The two-hour debate on ITV, presented by Julie Etchingham, will be the first time the two frontrunners will be able to cross swords with each other following the 90-minute audience questioning session, broadcast on Sky News on 26 March.

The debate will be broadcast the day after Labour and the Tories clashed over their policies on business and zero-hour contacts.

David Cameron and Ed Miliband
This will be the only occasion during campaign when Cameron and Miliband will debate against each otherReuters

All seven party leaders will be given an equal opportunity to speak during the broadcast. Each will be given a one-minute statement following each question before the discussion is opened up for around 17 to 18 minutes. None of the leaders will see the questions in advance.

After drawing lots, Green party leader Natalie Bennett will be the first to speak during the debate, with Cameron giving the final remarks.

The leaders will speak in this order

Bennett, Greens

Clegg, Lib Dems

Farage, Ukip

Miliband, Labour

Wood, Plaid Cymru

Sturgeon, SNP

Cameron, Conservatives

Some of the key issues expected to be discussed during the debate will include the "unprecedented" backing of the Tory party from over 100 business leaders and Labour's plans to outlaw "exploitative" contracts.

Cameron is also expected to use the debate to warn of the dangers that a left-wing coalition government could have on Britain.

Meanwhile, Miliband and Sturgeon, who may form a post-election coalition according to speculation in some quarters, will share a stage for the first time.

Nick Clegg and Nigel Farage debate
Nick Clegg and Nigel Farage clashed in a TV debate last year over the influence the EU has on UK lawGetty

Clegg, whose popularity surged to such an extent following 2010 televised debates that his party was able to form the coalition, is expected to emphasise that a hung parliament is inescapable and will urge people to vote on who else will govern the country along with the elected prime minister.

The Lib Dem leader will also highlight mental illness as a key issue after pledging more than £2bn of extra funding for mental health outlines in the party's "manifesto for the mind".

Ukip's Farage, who many believe will be the "winner" of this debate, is said to be preparing "rigorously" in order to make the most of the debate he desperately wanted against Cameron.

Ukip's campaign chief Patrick O'Flynn said: "Obviously this will be the only chance he gets to be on the same stage as David Cameron - and that's David Cameron's doing, not Nigel Farage's - so that again means that there will be key arguments to put there.

Ahead of the debate, a YouGov poll for The Sun put Miliband marginally ahead of Cameron - 36% compared with 35% for the Conservatives - with the Lib Dems on 7%, Ukip on 12% and the Greens on 5%.

Tv debate
SNP leader Nicola Sturgeon (C) the leader of Plaid Cymru, Leanne Wood, (L) and the leader of the Green Party Natalie Bennett (R) are also included in the debateGetty

Cameron will be keen to come across well in these debates, bearing in mind the rapid rise of Clegg in 2010 stopped his party from winning an overall majority in the last election.

Laurence Janta-Lipinski, associate director at YouGov, said: "There's a reason why Cameron was very opposed to having these debates, partly because he thought it distorted the campaign last time, but also because he's the man with everything to lose."