Three major broadcasters - the BBC, ITV and Sky - have agreed on the rules for hosting party leaders' debates in the run-up to the general election.
The three 90-minute sessions will begin by focusing on domestic policies, international affairs and the economy.
The studio audiences will then be able to ask direct questions on any subject, with viewers doing the same via e-mail.
Labour's Gordon Brown, Tory David Cameron and Lib Dem Nick Clegg agreed last year that they would appear.
The BBC is to hold separate party leader election debates in Scotland, Wales and Northern Ireland.
No handshakes
Unlike televised American presidential election debates, on which the the sessions are based, the prime ministerial candidates will not shake hands before or afterwards.
And applause will only be allowed at the beginning and end, to allow more questions to be asked.
"The agreement we are jointly announcing today represents a major step forward in the way election campaigns can reach the entire population"
Joint broadcasting panel
Mr Cameron said he welcomed the agreement, saying: "What this is all about is getting across is what we are passionate about."
Mr Clegg said: "We will be put under real scrutiny. Four-and-a-half hours is plenty of time to look at the leaders."
Mr Brown is expected to make a statement soon.
A spokesperson for the joint broadcasting panel said: "We warmly welcome the agreement by the party leaders to take part in these innovative programmes.
"We were delighted by the positive atmosphere in all our dealings with the parties over the last few months, and the agreement we are jointly announcing today represents a major step forward in the way election campaigns can reach the entire population."
The first debate, themed on domestic affairs, will be held in the north west of England, with ITV newsreader Alastair Stewart moderating.
The second, focusing on global issues, will take place in south west England, with Sky's political editor Adam Boulton in charge.
Time restrictions
And the third, broadcast by the BBC from the Midlands, will be moderated by Question Time host David Dimbleby and deal with the economy.
Mr Clegg will speak first in the first debate, with Mr Brown and Mr Cameron doing so in the subsequent sessions.
The sessions will be broadcast on weekday evenings, with the exact dates to be decided once the prime minister calls the election - it is widely expected to be held on 6 May.
The leaders' statements, answers and rebuttals are all subject to time restrictions - usually one minute, but with a longer closing statement of one minute 30 seconds at the end of each programme
The broadcasters have jointly appointed the market research company ICM to recruit an audience with a broad cross-section of views .
The BBC will be talking to the relevant parties in Scotland, Wales and Northern Ireland about the details of these debates.
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