Corbyn was joined at the debate by representatives of smaller parties, including Liberal Democrat leader Tim Farron and U.K. Independence Party chief Paul Nuttall.
But the Conservatives confirmed that interior minister Amber Rudd would represent the party as planned at the BBC hustings. "She won't turn up to these debates because her campaign of soundbites is falling apart". "By contrast, Theresa May's refusal to take part showed her weakness". "& Heartless", saying "Chicken" Theresa May "dodged" a debate with Mr Corbyn.
But buoyed by rising poll ratings - and the chance to make May look evasive - Corbyn changed his mind.
Voters were faced with a "very clear choice" on June 8, she said, adding: "That choice is about who is going to be prime minister, who is going to lead the United Kingdom in those Brexit negotiations, who has the plan to do that, the determination to get the best deal, who has the strong and stable leadership to do that".
She gave no answer, but said the election was a crucial choice, with her promising to negotiate the best Brexit deal for Britain when negotiations start with Brussels just days after the election. Farron said later. "The prime minister is not here tonight". The Labour leader was widely considered to have performed well in the format, prompting speculation about his participation in the leaders' debate.
The results of YouGov's model, published in The Times, suggested that the Tories could secure 310 seats, down from the 330 Mrs May went into the election campaign with, and 16 short of an overall majority.More news: British Airways flights return to skies, but reputation takes a hit
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Although the gap between the two big rivals, the Conservatives and Labour, has narrowed, May's party is still on course to win with a majority, but not necessarily the landslide predicted jut a few weeks ago when May called the snap election.
Setting out his pitch to voters, the Labour leader said: "We can not go on like this. A country that takes the decisions that matter to Britain here in Britain".
Corbyn recounted his TV appearance on Monday, in which he and May took questions from an audience and the presenter Jeremy Paxman.
The Financial Times announced its support for the Conservatives, but said "neither of the main party leaders is particularly impressive" and the lack of clarity from both sides on Brexit was "deeply unsatisfactory".
The prime minister would undoubtedly face questions over her leadership if the modelling by YouGov is proved to be accurate in just over a week, especially after she was forced into a humiliating U-turn over a proposed social care reformed dubbed the "dementia tax" by critics.
In a bid to return Brexit to the heart of the general election campaign, May will use a high-profile speech in the North East on Thursday to set out her vision of European Union withdrawal as a stepping stone to a successful future.