The House of Commons Speaker, John Bercow, has said he will “fight with every breath in my body” to stop Boris Johnson from proroguing parliament to force through a no-deal Brexit without the consent of MPs.

Bercow, who has previously said he did not believe it would be possible to suspend parliament to force through no deal, gave his strongest signal yet he was prepared to personally intervene to stop prorogation.

Speaking at the Edinburgh festival fringe, the Speaker said he would insist on the right of parliament to continue to sit and debate. “The one thing I feel strongly about is that the House of Commons must have its way,” he said. “And if there is an attempt to circumvent, to bypass or – God forbid – to close down parliament, that is anathema to me.

“I will fight with every breath in my body to stop that happening. We cannot have a situation in which parliament is shut down. We are a democratic society and parliament will be heard.

“Nobody is going to get away, as far as I’m concerned, with stopping that happening. Nobody should be afraid to say what he or she thinks.”

Asked by an audience member if parliament was able to stop a no-deal Brexit, Bercow replied: “Yes.”

Speaking in the Commons in June, Bercow warned the then-Tory leadership candidates that prorogation was not an option. “That is simply not going to happen. It is just so blindingly obvious that it almost doesn’t need to be stated, but apparently, it does and therefore I have done,” he told MPs.

Bercow’s interventions could be crucial in the coming weeks as MPs against no deal attempt to find a parliamentary route to blocking plans for the UK to exit on 31 October, with or without a deal.

A cross-party group are working on a plan to thwart Johnson, which could involve either forcing parliament to sit through the conference recess or amending the Commons motion that grants the September recess to allow them time to pass legislation against a no-deal Brexit.

Q&A What does 'prorogue parliament' mean? Show Prorogation is the official term that marks the end of a parliamentary session. After being advised to do so by the prime minister, the Queen formally prorogues parliament. This takes the form of an announcement in the House of Lords on the Queen’s behalf. It is a speech, written by the government, which usually describes the bills that have been passed during that session and summarises what has been achieved. It means that all work on existing legislation stops, and MPs and Lords stop sitting. Prorogation also automatically kills any bills, early day motions or questions to ministers going through parliament. Parliament can then be reopened a few days later with a fresh slate of legislation intentions, set out in a new Queen’s speech at the formal state opening of parliament.

Constitutional experts have said it is a plausible plan for cross-party rebels to seize control of the order paper via motions for recess, which are called “periodic adjournment motions”. They are not normally amendable, but Bercow caused major controversy in January when he defied this convention and allowed Tory MP Dominic Grieve to amend a similar motion.

Any amendment could suggest on a specific date or dates that “standing order 14 be set aside”, which is the order that gives the government precedence on business in the Commons – the tactic used to pass Yvette Cooper and Oliver Letwin’s bill against no deal in the spring. Dates could also potentially be reserved in late October.

Bercow’s comments came as a Scottish judge fast-tracked a legal challenge backed by 75 MPs and peers to prevent Johnson proroguing parliament, led by the Scottish National party MP Joanna Cherry QC.

The claim alleges it would be illegal and unconstitutional for the prime minister to suspend the Commons to prevent MPs blocking a no-deal Brexit before 31 October. An urgent hearing of the case will place on Friday 6 September, the week parliament returns from recess.