Boris Johnson urges EU to get on with 'serious' negotiations on trade

He spoke as the Prime Minister prepared for a showdown with chief negotiator Michel Barnier and Commission president Jean-Claude Juncker, just days after they said exit negotiations were deadlocked.

Downing Street sources insisted the meeting had "been in the diary for weeks" but the announcement caused surprise in Westminster and comes after last week's negotiations ended with little movement.

Mrs May, who will be joined by Brexit Secretary David Davis, is expected to have discussions with European counterparts over the coming days ahead of a meeting of all EU leaders later in the week.

Over dinner, the PM will hope to end the stalemate over the divorce settlement that is stopping a post-Brexit trading relationship being discussed.

After the fifth round of discussions were brought to a close last week, Mr Barnier said he would not recommend that talks move on to the next stage when he attends the European Council on Thursday.

But arriving for a meeting of EU foreign affairs ministers in Luxembourg, Mr Johnson said: "We think in the UK that it's time to get on with these negotiations.

"It's ready for the great ship to go down the slipway and on to the open sea and for us to start some serious conversations about the future and the new relationship, the deep and special partnership that we hope to construct, and I think will work very much in the interests of both sides.

"And people say to me, look, we want to reassure the 3.2 million EU nationals in the UK and the one and a bit million UK nationals in the EU, and so do we.

"We've made a very good offer, we've made a very fair (offer), and we think it's a reasonable point of view that we're outlining.

"Let's give them that reassurance, let's put a tiger in the tank, let's get these conversations going and stop letting the grass grow under our feet.

"We hope very much that our friends and partners will take that message and really begin some serious negotiations."

Last week, Mr Barnier said negotiations had ended without making any "great steps forward" and there was "disturbing deadlock" over the size of Britain's divorce bill.

Mr Juncker said the Brexit process will take "longer than we initially thought", blaming delays on Britain's failure to settle its financial obligations.

The Government wants EU leaders to expand Mr Barnier's negotiating mandate to allow some headway to be made.

The stalemate has left Mrs May under pressure from Brexiteers to prepare for a "no deal" withdrawal to show the UK is serious about walking away from talks, in the hope this could bounce the EU into action and push them forward.

But opposition parties and Remain-backing Tories have warned Parliament could stop the Government taking Britain out of the EU without an agreement in place.

Shadow chancellor John McDonnell has suggested Tory MPs are in talks with Labour over bids to change the EU (Withdrawal) Bill to give Parliament a veto over a no deal exit.

But amid concerns Tory rebels may not back proposals from Labour's frontbench, former chancellor Ken Clarke said his amendments to the Bill are designed to tie the hands of "ultra-left" shadow cabinet members as well as "ultra-right" Cabinet ministers.

Asked if Parliament had the power to veto a no-deal option with the consequence Britain would remain in the EU, Mr Clarke told BBC Radio 4's Today programme: "As an off-the-cuff constitutional legal reply, yes, it does. This is a parliamentary democracy, Parliament here can do, practically, what it likes.

"But a majority, I think, would wish to look in the round at whatever this crisis scenario is that has arisen at the time."

Mr Clarke said a no deal situation would be "catastrophic" for the UK economy in the short term.

In what is likely to be seen as a dig at Mr Johnson, he said: "We mustn't be seduced by this bizarre stuff of the lion roaring, and of President Trump, and the Japanese, and protectionist countries around the world, all being prepared to open their markets to us, no rules we have got to comply with, and no obligations. Just 'come and sell us whatever you want'.

"This is compete fantasy. It's la-la land. It's going down the rabbit hole with a white rabbit."

Downing Street denied that the dinner was a panicked reaction to recent developments, insisting that it had been in the PM's diary since around the time of her speech in Florence in late September.

Mrs May was also expected to speak by phone on Monday to French President Emmanuel Macron and Taoiseach Leo Varadkar before departing for Brussels for the dinner, due to start at 6.30pm local time and last around 90 minutes.

The PM's official spokesman said that Brexit would not be the only item for discussion during the dinner or the phone calls, suggesting that the Iran nuclear deal, counter-terrorism and internet extremism would also come up.

Also attending the dinner are Number 10 Brexit adviser Olly Robbins and Mr Juncker's chief of staff Martin Selmayr.

Mr Selmayr was widely blamed for leaking details of a previous private dinner at Number 10 in April, when Mr Juncker reportedly said he left "10 times more sceptical" than when he arrived.

The leak led to an angry response from Mrs May on the steps of Downing Street in which she warned that "there are some in Brussels who do not want these talks to succeed".

Asked whether Mrs May had demanded assurances that there would be no repeat of the leak after Monday's dinner, the PM's official spokesman told reporters: "The Prime Minister has had a number of constructive conversations with Jean-Claude Juncker. We expect this to be a constructive dinner."

Mr Juncker declined to comment on his expectations for the dinner, but suggested that details of their discussions would be revealed in a "post mortem" after it has concluded.

Asked about the dinner at a press conference in Brussels, the Commission president said: "I have never understood why journalists - even the most eminent journalists - ask for the outcome of a meeting before the meeting takes place.

"Yes, I'm going to see Mrs May tonight. You are going to have the report of it, it will be a post mortem report."