Anti-Brexit campaigner Gina Miller has said the British government "unequivocally" accepts that it cannot close down parliament to allow a no-deal Brexit.
The businesswoman, who last month wrote to Prime Minister Boris Johnson arguing any move to prorogue parliament "would be an abuse of his powers" and would result in legal action, said she had been reassured parliament would not be suspended.
Ms Miller previously went to court and won the right for parliament to give its consent ahead of the government triggering Article 50 to begin the Brexit process.
She told Sky's Sophy Ridge On Sunday: "What they have said is unequivocally they accept that to close down Parliament to bypass them in terms of Brexit - stopping a no-deal Brexit in particular - is illegal.
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"So without having to go to court they've conceded we've basically called their bluff."
But Ms Miller said that whilst the government had given a reassurance that Parliament will not be prorogued, she said she would be seeking further reassurance that MPs would be able to pass legislation to stop a no-deal Brexit.
She said: "At the moment parliament has to find a way - instruments and ways - of ensuring that they can pass that legislation, scrutinising which is what the Government letter has confirmed, that Parliament will be able to scrutinise and examine all options when it comes to exiting, it's not the same as giving them the ability to pass legislation.
"And because we already have in legislation that October 31 is our exit they need to pass other legislation to prevent no-deal or to change that date after an extension."