Conservative leadership candidate Dominic Raab has insisted he will not rule out the option of suspending parliament to stop MPs blocking a no-deal Brexit.

Mr Raab has been accused of risking dragging the Queen into politics by wielding the threat of prorogation, under which the prime minister goes to the monarch with a request for parliament not to sit until a certain date.

But he said it was crucial to keep all negotiating tools on the table to ensure the UK leaves the EU on 31 October as planned.

Mr Raab said that a commitment to meeting the Halloween deadline, and even being prepared to leave without a deal under World Trade Organisation rules if necessary, was a “test of nerve” for the contenders to replace Theresa May as prime minister.

Rivals including Jeremy Hunt and Michael Gove have said they would be ready to ask for a further extension of talks in order to secure a deal with Brussels.

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In an apparent swipe at frontrunner Boris Johnson, who has so far kept a low profile in the leadership race, Mr Raab said that all candidates should set out their Brexit positions clearly and be subject to scrutiny in interviews.

Speaking to BBC Radio 4’s Today programme, Mr Raab said it was “very unlikely” that prorogation would be needed.

But he added: “It is wrong to rule out any tool to make sure that we leave by the end of October.

“I think anybody who is talking about delay or is taking WTO off the table is having a perverse effect of weakening our negotiating position in Brussels.”

Mr Raab said that any suggestion the UK would countenance a delay in order to avoid no-deal would lead to Brussels officials thinking, “We have a chance to lure them into the cage of a customs union or a more restrictive legislative high-alignment model”.

He continued: “If we started suggesting we are not really sure we will be leaving at the end of October, we send them the message that they don’t need to focus their minds, we are not really serious.

“That’s a strategic mistake and I don’t think any of the candidates should fall into that trap.”

The former Brexit secretary said he would go back to Brussels with a “best, final offer” but if that did not work he would leave without a deal.

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He added: “What we can’t have is this paralysing uncertainty, bad for the economy, bad for trust in democracy, bad for the Conservatives – as we are seeing – of just going on and on with this prolonged torture of haggling with the EU when we haven’t got a deal in sight”.

Mr Raab said that in his four months as Brexit secretary last year, he was “the negotiator that pushed them the hardest and dared say things that no one had dared”. He repeated his claim that he could have secured a deal if he had been “backed up” by others in government.

And he said: “All candidates should be honest about their plans and be subject to scrutiny, because it’s a test of nerve here, and if candidates can’t stand up (for) their resolve to lead us out by the end of October in a leadership contest, what chance would they have in the heat of negotiations in Brussels?”

Asked whether he would serve in a government led by Mr Johnson, Mr Raab said: “Of course. It would depend slightly on what was being offered – you have got to be willing, able and good at doing the job you have been offered.