Party says proposal is compatible with tight timetable for Brexit, though deal would need to be agreed within nine months

Britain could have a second EU referendum as an early Christmas present in 2018, the Liberal Democrats have said, proposing a lengthy 12-week campaign starting in September to give the UK the option to accept a deal or stay in the EU.

The party said holding a referendum on the final deal – which the government has repeatedly ruled out – in December was compatible with the tight timetable of EU withdrawal, falling within the article 50 timeframe of two years, which will end in March 2019.

The Lib Dem leader, Vince Cable, said a referendum should be timed to coincide with EU states’ own votes on the final agreement.

The party’s proposed timing for a referendum would mean a final deal needing to be agreed in time for campaigning to kick off in September, just nine months away.

Critics have argued that a second referendum would be an incentive for European leaders to give the UK a poor exit deal. Theresa May said in the Commons on Monday that promising a referendum would “actually be betraying the British people”.

Cable said there was growing public support for a referendum on the final deal, citing a recent poll by Survation that found 50% of respondents wanted a vote.

“This potential timeline to a public vote shows Brexit is not a done deal. It can be stopped, but not without the approval of the British public,” he said. “It’s time the Conservatives – and the Labour leadership – listened.”

The party proposes a timetable for a referendum beginning when the EU withdrawal bill is given royal assent in April 2018. It has proposed an amendment to the legislation, to be debated on Wednesday, which would give a final vote on the deal to the British public. The amendment is highly unlikely to pass.

The party’s proposed timetable is:

April 2018: government introduces a referendum on the deal bill.

May 2018: referendum on the deal bill receives royal assent



September 2018: a 12-week referendum campaign begins, with a vote scheduled for early December.



September-December 2018: the European parliament votes on the final Brexit settlement, and the European Council approves the deal.



December 2018: the referendum, and a parliamentary vote to adopt the result. If remain were to win, the government would formally withdraw from the article 50 process.

Cable said his party would campaign to remain in the EU regardless of the outcome of the Brexit negotiations, as any deal agreed could not have better terms than full membership.