Rishi Sunak and Sir Keir Starmer clashed over migration and the betting scandal that has engulfed Westminster in their final televised head-to-head before polling day.
The Prime Minster asked the Labour leader if he was planning to make a deal with the Taliban to send back asylum seekers rejected from the UK in a spiky exchange over the small boats crisis.
In response to a question from the BBC audience, Sir Keir said his government would "smash" the human trafficking gangs profiting from people making the perilous journey across the Channel.
He repeated his pledge to scrap the Tory plan to send some migrants to Rwanda if Labour wins the general election and argued that his government would process arrivals more quickly and develop returns deals.
But Mr Sunak hit back and said: "The migrants are coming from Iran, Syria and Afghanistan.
"Will you sit down with the Ayatollahs? Are you going to try to do a deal with the Taliban? It's completely nonsensical - you are taking people for fools."
Sir Keir added that over 50,000 people have arrived in the UK by crossing the Channel since Mr Sunak became Prime Minister.
This includes a record more than 13,000 this year alone, Home Office figures show.
Sir Keir later denied claims from Mr Sunak that a Labour government would allow "free movement by the back doors".
"We are not going back into the EU, we're not rejoining the single market or customs union, and we're not accepting freedom of movement," he said.
"I'm not a defeatist like the Prime Minister."
To applause, he added: "I know we can get a better deal than the botched deal that we've got and I'm going to go out and fight for it."
The row surrounding political bets placed on the timing and results of the election also featured heavily in the last major setpiece event before polling day on July 4.
The debate, chaired by the BBC's Mishal Husain, kicked off with Sir Keir accusing the Prime Minister of being "bullied" into taking action over the Westminster gambling scandal.
The first audience question was about how the leaders would restore trust in politics, with people "dismayed by the lack of integrity and honesty" amid the recent allegations.
Sir Keir laid the blame at the Prime Minister's door.
At least five Conservatives are being investigated by the Gambling Commission as part of its inquiry into wagers on the July 4 poll.
Sir Keir said: "You have to lead from the front on issues like this."
He also linked the scandal to partygate, when Mr Sunak was fined for breaking lockdown rules during the pandemic.
"What I did, when one of my team was alleged to have been involved and investigated by the Gambling Commission, they were suspended within minutes, because I knew it made it really important to be swift.
"The Prime Minister delayed and delayed and delayed until eventually he was bullied into taking action."
Mr Sunak responded: "It was important to me, that given the seriousness and the sensitivity of the matters at hand that they were dealt with properly, and that's what I've done."
The Prime Minister repeated that he was "frustrated" and "furious" about the affair.
He hit back at the Labour leader by launching an attack on his tax plans, saying Sir Keir "is not being honest with everyone about his plans to raise their taxes".
A YouGov snap poll found there was no winner in the debate.
In a survey of 1,716 viewers, 47% said Sir Keir won, 47% said Mr Sunak did, and 6% answered they did not know.
However a second poll declared Sir Keir the winner.
In a More in Common survey of 1,525 viewers, 56% said the Labour leader won, whereas 44 per cent said the Prime Minister did.
Of the respondents, 30 per cent said Mr Sunak performed better than expected, compared to 19 per cent saying the same for Sir Keir.
