Ed Davey, who has just launched a Lib Dem leadership bid, says he will call on the Queen to require the prime minister to revoke Article 50 if the country reached a no-deal cliff edge.
The Kingston and Surbiton MP said he would propose a “cross-party humble address to Her Majesty”.
He added that he hoped Jeremy Corbyn would join in with the address.
A humble address is a direct communication from the House of Commons to the Queen, calling on the government to comply with a request.
If approved, humble addresses are considered binding.
In November 2017, Labour used a humble address to force the government to publish 58 studies into the economic impact of Brexit.
Sir Ed added: “Under my leadership, the Lib Dems will continue to lead the fight to stop Brexit, nothing is more urgent in British politics today.”
The party claimed 20% of the vote and won 16 MEPs in the European elections, boosted by a strong pro-EU message.
A leadership race is currently under way, likely to be between Davey and Jo Swinson, with Vince Cable’s replacement to be decided by July 23.
READ MORE: Who’s who in the Liberal Democrat leadership contestThe former energy and climate change minister also paid tribute to Cable, calling him a “giant of British politics and the economy”.
Praising one of the party’s EU election campaign slogans, he added: “‘Bollocks to Brexit’ was correct and courageous.”
Sir Ed also set out plans to tackle climate change and “de-carbonise capitalism, to turn capitalism green”.
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