Tim Farron will launch a brutal attack on Theresa May later today when he uses his conference speech to demand she come clean on her plan to take Britain out the EU.

Three months after the referendum result which sent shockwaves through UK politics, the Lib Dem leader will ask why the prime minister has still not provided any details of her plan.

"Nearly three months since the referendum and we have a government with new departments, new titles, a new prime minister – but no plan, no vision, no clue, and no leadership,” he is expected to say.

"The absence of leadership from Theresa May is astonishing, the absence of clarity as to what will happen to our country is a disgrace. 

"Theresa May – tell us what Brexit really means.

"You've had three months. You are the prime minister. Act like a prime minister. What is your plan?"

The comments come in a speech which will reiterate the Liberal Democrat pledge to hold a second referendum on Brexit once the terms of the deal have been finalised with the EU.

Many commentators believe that deal could take several years to thrash out, but the Article 50 process only lasts two, leaving a high degree of uncertainty in Westminster and Brussels about the logistics of the Brexit process.

"The Liberal Democrats have a plan," Farron is expected to say.

"We know what we want and we know where we want to take our country.

"When Theresa May does agree a deal with the EU, we want the people to decide.

"How dare they let bureaucrats in Whitehall and Brussels stitch up our future?

"If we trusted the people to vote for our departure then we must trust the people to vote for our destination.”

Farron's policy of holding a second referendum was easily passed at conference yesterday, but there is an increasingly public split among senior figures on the issue.
Former business secretary Vince Cable branded the policy "utterly counterproductive".

"There are people in the party who don't accept the outcome, who feel incredibly angry and feel it's reversible, that somehow we can undo it," he told a fringe event.

"The public have voted and I do think it's seriously disrespectful and politically utterly counterproductive to say: 'Sorry guys, you've got it wrong, we're going to try again,' I don't think we can do that."

He warned that the policy prevented the party from campaiging for a soft Brexit, which would keep the UK in the single market, and put the Lib Dems in the same camp, on a practical level, as Ukip.

"We should be very careful about the company we keep," Cable said.

Former leader Paddy Ashdown struck a similar note when speaking to reporters.

He said: "Your presumption is that all the 48% who voted to remain in Europe would want to see a second referendum. I don’t think that’s true. I think there’s a huge number of them, who think 'OK, it's out, we don't want to re-run that, but we do want the right solution.'"

Former leader Nick Clegg expressed his support, however.

"I think Tim's absolutely dead right," he said.

"The call he's made is one of those that will get a bit of criticism to begin with, but will be vindicated over time".

The prime minister has ruled out a second referendum, a parliamentary vote on triggering Article 50, or even making her Brexit plans public until after Article 50 has been triggered.

But some former Remain supporters are hoping that a protracted negotiation process and negative economic news could swing the public mood against Brexit and force the government’s hand on holding a second vote.