Political parties and broadcasters are engaged in a bitter round of recriminations after the final line-up of televised election clashes was announced.
David Cameron has been accused of "cowardice" by Labour after agreeing to appear in a single seven-way debate on April 2, but shunning a head-to-head against Ed Miliband.
The Prime Minister and Mr Miliband will be interviewed and answer questions from a studio audience on a Sky News/Channel 4 programme next Thursday - but will not have any direct exchanges.
Mr Cameron, Mr Miliband and Liberal Democrat leader Nick Clegg will also feature separately in a BBC Question Time special on April 30, just a week before the nation goes to the polls.
The only other true debate of the campaign will take place on ITV on April 16, and pit Mr Miliband against Ukip's Nigel Farage, Natalie Bennett of the Green Party, Nicola Sturgeon of the SNP, and Leanne Wood from Plaid Cymru.
The final line-up follows years of wrangling between parties and broadcasters over whether and how to repeat the debates from the 2010 election campaign - which saw Gordon Brown, Mr Cameron and Mr Clegg square up three times.
Mr Cameron rejected previous proposals on the basis they did not include the Greens, and insisted the sessions should not take place during the short election campaign that starts on March 30.
However, last week he appeared to surprise other parties and the broadcasters by declaring that he had accepted plans for the seven-way debate on April 2 and would participate in a variety of other programmes.
A Tory source insisted they had secured an even better deal than they were hoping for.
"If anything this is an improvement on the deal we were offered last week," they said. "The PM has always believed too many debates would suck the life out of the campaign.
"In all these formats, we are confident the choice between competence and chaos will be clear."
A Labour Party spokesman accused Channel 4 and Sky News of backing down on a pledge to "empty chair" Mr Cameron.
They also complained that the Prime Minister had been allowed to "veto" Mr Clegg's participation in the debate on April 16.
"After weeks of pressure from the Conservative Party, Channel 4 and Sky have indicated to us that they are unwilling to stick to their commitment of March 6 to proceed with the head-to-head debate programme if David Cameron refused to take part," the spokesman said.
"We have therefore, and with great reluctance, agreed to a change in the format of the programme on the April 30.
"David Cameron and Ed Miliband will now attend the same programme and take the same questions from the same audience.
"But due to the cowardice of David Cameron the two leaders will not be on stage at the same time to debate each other.
"The Conservative Party has also objected to the second debate on April 16.
"We have made clear we will attend this second debate. But, again at the Conservative Party's insistence, Nick Clegg is to be excluded.
"The whole country will understand the reasons for this: the Prime Minister wants to minimise the scope of televised debates between himself and Ed Miliband.
"We hope that even at this late stage David Cameron will rethink both his decision not to take part on April 16 and to veto Nick Clegg's participation."
Mr Farage said the broadcasters should be "ashamed".
"They've kowtowed to manipulation from Downing Street and are now offering a shoddy selection of alternatives that are no different from typical election coverage already taking place," he said.
"Clegg should take part in the so-called 'Challengers' Debate' and not be so weak as to be bought off by the Conservatives.
"As for the ridiculous proposal to replace one debate with a Question Time style event with the major party leaders it simply cannot be justified to exclude Ukip when just this week we were given major party status by Ofcom."
He added: "The entire plan has been concocted by the broadcasters in collaboration with the Conservatives. How we can ever again laud having transparent and neutral public service broadcasting in this country following this debacle I do not know.
"The general public wanted and rightly deserve proper, open General Election leaders' debates between the main parties, but instead are being fobbed off with a total rehash that plays into the hands of one man and one party only. It's a smack in the face of democracy and I am appalled."
A Liberal Democrat spokesman said: "We have told the broadcasters that we will take part in the proposed format, just as we have said we would take part in all the proposed packages to date from the 4-3-2 original format, to the 7-7-2 format and all other permutations, despite our strong objections to being excluded from any TV debate or interview.
"If it was down to us, we would be in every TV debate and every interview and are ready to take part in any of them.
"But we think that the politicians and broadcasters have ducked and dived on this long enough and just need to get on with it now and ensure the public have the opportunity, however flawed the format, to scrutinise their politicians."
Green Party leader Natalie Bennett said: "I welcome the fact that we now finally appear to have reached the end of the debate about the debates.
"David Cameron's intransigence has delayed this process, and taken away space in which we might have been debating the future of Britain - our low-pay, insecure jobs, the privatisation of our NHS, the urgency of cutting carbon emissions.
"Nonetheless, we can now move on, in the new age of multi-party politics in Britain."
A joint statement from the broadcasters said: "We're delighted that there will be a debate with all the party leaders during the election campaign. The debate on April 2 will build on the success of the 2010 TV debates which were so highly valued by viewers.
"We're very pleased to be able to offer viewers an extensive range of programmes, across the four channels, featuring the party leaders interacting directly with voters during the campaign."
Mr Miliband said: "David Cameron is now in the ridiculous position where he'll go to the same studio as me, on the same night as me, with the same audience as me but he won't debate me head to head as he's running scared.
"I'm going to keep the offer of a head to head debate on the table right up to Election Day as it's what the British people want and what they deserve."
Plaid Cymru leader Leanne Wood said: "No politician should be able to choose whether to be held accountable or not and it should not be a choice for a prime minister.
"Though it falls short of the original proposals, I welcome this statement from the broadcasters. There is demand for these debates because people want to hear from the parties that could have a major impact on the next UK government.
"It's important that people in Wales, and the other nations in the UK, are presented with a true reflection of the choice facing them on May 7.
"I look forward to representing the Party of Wales as a strong voice for Wales in these debates."
SNP leader and First Minister Nicola Sturgeon said: "The SNP have always said that we will take part in General Election debates anytime and anywhere, and look forward to doing so.
"Our preference would have been for broadcasters to stick to their original proposals, and not be pushed around by the Westminster parties, particularly the Tories. However, it is good that the debate about the debates is finally over and we can get on to discussing the real issues of substance.
"The next House of Commons looks likely to be a hung parliament, and the SNP are working hard to deliver a strong voice for Scotland with a team of MPs, who in turn could influence the governance of the whole UK.
"That is an important part of the context of this election - and the broadcasters have a duty to their audiences north and south of the border to ensure that all of their election programmes reflect the range of democratic choices available and likely outcomes."