Liberal Democrat leader Sir Vince Cable will use his keynote speech at his party's autumn conference to call for "political adults" on all Commons benches to join forces with him and try to reverse Brexit.
He is challenging Foreign Secretary Boris Johnson and other 'Brexiteers' to defend any deal hammered out with Brussels in a new referendum.
Speaking in Bournemouth, Mr Cable will say: "What are they afraid of? Are they afraid that the claims of £350 million a week for the NHS won't wash any more?
"That claim has rightly been dismissed by the UK Statistics Authority. No wonder Boris and the Brexiteers are so afraid of the people, and the facts.
"They now believe in the slogan of dictators everywhere: 'one person, one vote, once'.
"We believe the public have a right to change their mind."
As he calls for a cross-party effort against a hard Brexit, Mr Cable will say: "What the country now desperately needs is some political adults.
"There are sensible grown-ups in the Conservative Party, and the Labour Party and the Greens.
"We have to put aside tribal differences and work alongside like-minded people to keep the single market and customs union, essential for trade and jobs."
He is also set to accuse Labour leader Jeremy Corbyn of trying to face both ways on Brexit.
The Lib Dem leader will tell the conference: "He would do better to get off the fence and refurbish his revolutionary credentials. Jeremy - join us in the Anti-Brexit People's Liberation Front."