Tony Blair, Michael Howard and Charles Kennedy have agreed to appear on the same edition of Question Time.
The special falls some way short of a US-style debate
The special episode will be the nearest the UK will come to having a US presidential-style debate between the prime minister and his rivals.
Full details are yet to be agreed but they are expected to be questioned one after another by the same audience in a programme chaired by David Dimbleby.
Plans for head-to-head leader debates have always failed in recent years.
In 1997, plans for a debate between Mr Blair and John Major foundered and a three-way debate between Mr Blair, Mr Kennedy and William Hague also came to nothing in 2001.
Mr Howard said in October last year that Mr Blair would be "running scared" if he did not agree to a full debate this time around.
When he was under pressure to agree to a live debate in 2001, then Leader of the Commons, Margaret Beckett, defended Mr Blair's decision, saying TV debates were "geared to an American-style election" and would focus attention on the individuals rather than the political parties.
The sequential interviews fall way short of the US model, where the Republican and Democrat candidates do battle in a series of themed sessions.
The BBC's coverage will also feature interviews with the three leaders by Newsnight anchor Jeremy Paxman to be broadcast on BBC One at primetime.
This year's election is the first with broadband and interactive television a commonplace option for the audience.
There will be extended times for BBC One's Ten O'clock News and BBC Radio 4's The World at One. Election night coverage on television will be presented by David Dimbleby, with Radio 4 having James Naughtie and Carolyn Quinn as its anchors.
The more innovative ways of covering the poll include Newsnight's Michael Crick travelling the country in a helicopter, and The Politics Show doing the same in a narrowboat.