The EU has piled further pressure on Britain to settle its “divorce bill” and the fate of EU citizens after Brexit – demanding answers within five days.

Michel Barnier, the EU's chief Brexit negotiator, also ridiculed Boris Johnson’s claim that the EU could “go whistle” over the multi-billion pound exit settlement.

“I'm not hearing any whistling, just the clock ticking,” Mr Barnier told a Brussels conference - underlining where the power lies, in his view.

The second round of the withdrawal negotiations will get underway next Monday, bringing Mr Barnier face-to-face with Brexit Secretary David Davis again.

But the chief negotiator said he wanted clarification “before the beginning of the second round” – making clear he was willing to work through the weekend to make progress.

Mr Barnier also insisted he was not trying to push Theresa May into walking out of the talks by requiring the continued jurisdiction of the European Court of Justice, including over the rights of citizens.

“I don’t want to push anybody over the edge, but we have to find clear and sustainable solutions,” he said.

Laying bare the dispute on citizens, he added: “The British position does not allow [EU citizens in UK] to continue to live their lives as they do today.”

And, setting out the difficulties ahead, Mr Barnier said: “How do you build a relationship based on trade and security to last with a country where you don't have trust?”

Until now, it had been thought that EU leaders would be satisfied provided Ms May – if she survives in office – set out the UK’s detailed position at a summit in October.

Mr Barnier’s comments came as credit ratings agency Moody's warned that Britain would face “materially weaker” growth if it failed to secure a good deal on trade after Brexit.

Last month, Mr Davis caved in to the EU’s demand for citizens’ rights, the size of Britain’s “divorce bill” and border issues to be settled at the outset of the negotiations.

He was forced to drop his central demand for talks on future trade – Britain’s priority – to be staged in parallel, within hours of arriving in Brussels.

The negotiations would only move onto trade when the EU decided “enough progress” had been made on its three priorities, Mr Davis conceded.

That sets the scene for an autumn row, after Tory backbenchers lined up to insist the Prime Minister must not agree to pay a penny as the price for Brexit.

But Mr Barnier attacked British politicians who have described the financial settlement as a “ransom” – insisting the EU was “simply settling accounts”.

“It's not an exit bill. It is not a punishment. It is not a revenge. At no time has it been those things,” he said.

He made clear the EU would not discuss anything else without progress on its three priorities, which were “indivisible and intertwined”.

Before meeting Mr Davis on Monday, Mr Barnier will hold talks with both Jeremy Corbyn and Nicola Sturgeon and Carwyn Jones, the leaders of Scotland and Wales respectively.