Formerly fringe issues such as EU membership and nuclear missiles will likely feature in unprecedented seven-way debate.
The contest comes before an unusually close national election on May 7.
Bubbling under the UK's general election campaign is a promised referendum on EU membership. Is Britain heading for the way out?
Britain's continued membership of the European Union hangs on the outcome of the election on May 7.
Miliband said he is a "resilient guy" and believes he has been underestimated.
Polls suggest Scottish National Party could form third biggest party in UK Parliament after May 7 election.
Three Labour candidates have now rejected their share of £100,000 Tony Blair donated to the Labour campaign.
Opinion polls show the SNP is set to take dozens of seats from the Labour Party in Scotland.
A new model predicting the outcome of the election produced a 94.5% chance of a coalition government.
The Times/YouGov poll shows the Scottish National Party would take 48% of the vote to Labour's 27%.
An annual report comparing healthcare across Europe shows Britain falling from 14th to 16th.
Blair said the election could be a traditional left versus right contest "with the traditional result"
The poll confirms a seismic shift in Scottish politics away from the Westminster parties
Tony Blair's father-in-law is on typically robust form talking about the making of a prime minister, politics and mortality
The three parties announced an alliance aimed at ending the mainstream 'obsession' with austerity and getting rid of Trident
The 'Campaigning Against Ukip' document advised against discussing immigration in favour of "issues where we have a clear policy"
According to the Institute for Fiscal Studies, there are now major differences between the two parties spending plans
Eyeing renewed devolution, Yorkshire, with a bigger population than Scotland and bigger economy than Wales, wants to be next
The divide between Lib Dems and Conservatives is growing rapidly as the general election approaches
A thinktank says the public is facing a "candour deficit" as parties keep plans vague
Bookies Paddy Power predict a Reckless win in Rochester and Strood as 75% of bets back Ukip
Leader of the opposition party Ed Miliband has he will not "shrink from the fight" in a make-or-break speech after poor poll numbers and rumours of leadership plots
Conservatives take 3 point lead as Miliband revealed as one of the most unpopular party leaders of all time in latest Ipsos Mori polls
Ed Miliband is facing fresh pressure after a poll revealed a fall in support from supporters of his own party
Ed Miliband described media reports that members of his own party were conspiring to oust him ahead of the general election as "nonsense"
41% of the British eurosceptic party's supporters said they believed that 'a house could be haunted', while Labour supporters were more likely to believe in vampires