In the first televised debate of the campaign, the five candidates taking part taunted Boris Johnson for failing to turn up.
Channel 4, which staged the debate, put an empty podium for Johnson who refused to take part.
Host Krishnan Guru-Murthy said Johnson had declined the invitation but was “welcome” to join at any point, adding ther was still time for him to “get a taxi from north London”.
His absence was raised in the debate by foreign secretary Jeremy Hunt who said it raised questions about his ability to take on the job of prime minister.
“Where is Boris? If his team won’t allow him out with five fairly friendly colleagues, how is is he going to deal with 27 European countries?” he said.
Earlier in the day Rory Stewart said there was a “problem of trust” with politics, and that Johnson’s failure to attend was a part of this.
“He keeps saying “I am going to deliver it.” I don’t even know what he believes.
“He won’t talk to me. He won’t talk to you. He won’t talk to the public.”
The sharpest exchanges were however dominated by Raab’s insistence the option of proroguing parliament should remain on the table.
“I don’t think it is likely but it is not illegal,” he said.
“The moment that we telegraph to the EU we are not willing to walk away at the end of October we take away our best shot of a deal.”
International development secretary Rory Stewart said shutting down parliament was “undemocratic” and “deeply disturbing” and would not work.
“Parliament is not a building. Parliament is our democratic representatives and they will meet regardless of what the prime minister wants,” he said to applause from the studio audience.
Hunt said it was the “wrong thing to do” while home secretary Sajid Javid said: “You don’t deliver democracy by trashing democracy. We are not selecting a dictator.”
Raab warned that parliament could not stop a determined prime minister, saying: “It is near impossible to stop a government that is serious.”
That drew a sharp retort from environment secretary Michael Gove who told him: “I will defend our democracy.
“You cannot take Britain out of the EU against the will of parliament.”
All of the candidates, except for Stewart, said that they would be prepared to leave the EU without a deal.
He said that it was not a credible threat because the EU was aware of the damage it would do the UK.
“We are not going to get a different deal from Europe,” he said.
“A no-deal Brexit is a complete nonsense. It is going to deeply damage our economy,” he said.
Javid said it was a “complete nonsense” to take away the threat of no deal although he acknowledged not enough had been done to prepare for it.
“The number one mistake that was made was not planning for no deal. I have never walked into a room without the ability to walk away without signing.”
Hunt said the next prime minister had to be prepared to sit down and negotiate with Brussels to get a better deal than that negotiated by Theresa May.
“It is fundamentally pessimistic to say we cannot do that,” he said.
Gove said that he had the experience to renegotiate the controversial Northern Ireland backstop which proved the key stumbling block to getting Mrs May’s deal through parliament.
“I would ensure we have a full stop to the backstop,” he said.
Raab, who quit as Brexit secretary over May’s agreement, said that as a committed Brexiteer he could be relied on to deliver Brexit.
“I believe I am the candidate most trusted to get us out of the EU by the end of October,” he said.
Apart from the clashes over Brexit, there were few sharp exchanges with the candidates being notably polite – and at times even friendly – towards each other.
When Gove was questioned about his admission of past cocaine use Hunt stepped in to defend him.
“Every one of us has done something 25 years ago we wouldn’t want our mum and dad to find out about,” he said.
“When we face a constitutional crisis of the magnitude of Brexit, we should not be trivialising this debate by talking about what we got up to 25 years ago.”
Gove in turn defended Javid when presenter Krishnan Guru-Murthy suggested he had not been invited to the state banquet for Donald Trump because he was “not a big enough figure”.
“Saj doesn’t need Donald Trump to tell him he is a big figure. He is a hero,” Gove said.
Asked if the country was ready for a British-Pakistani prime minister, Javid said: “I think the country is ready for anyone to be prime minister so long as they have the talent and experience to do the job.”