Michel Barnier is due to meet with former Lib Dem leader Nick Clegg, the Labour peer Andrew Adonis and Tory big beast Ken Clarke this afternoon for hush-hush discussions in the Belgian capital.
The three will also talk to the EU’s Commissioner for economic and financial affairs, Frenchman Pierre Moscovici, during a trip which will raise further fears over Remainers trying to undermine Brexit.
Eurocrats today defended the pair over the meetings, saying that they had been requested by the British trio and that the bloc will only ever negotiate with the official UK Government.
But eurosceptics have long feared a “Remainer coup” where prominent europhiles try to sow division in Westminster and Brussels to topple Theresa May and pursue a soft Brexit or even reversal of the referendum.
Independent MEP Steven Woolfe told express.co.uk: “This looks extremely suspect. It is a deliberate, underhanded attempt by a group of Remainers to undermine the official negotiations being conducted by the David Davis and the leave vote last year.
“Frankly. it’s a distraction and is certainly not done in the interests of the UK, but rather in the interests of themselves.”
Former Ukip leader Nigel Farage added: “It’s like an Unholy Trinity going down and desperate to undermine the democratic Brexit vote. Especially so, as Clegg has no electoral mandate.
“That Michel Barnier is even meeting them shows those in Brussels cannot be trusted in these negotiations at all.”
And Ukip MEP Gerard Batten said: “This is outrageous. None of these men are currently elected to anything and have no right to pretend to represent the British public is this matter.
“Having them go to Brussels is like Oswald Mosely and Lord Haw-Haw going to Berlin to negotiate peace terms in 1940”.
Last week reports emerged that senior europhile Tories are planning to go over Mrs May’s heads and seek direct talks with Brussels in a bid to steer Britain towards staying in the Single Market.
Officials said the three are due to meet Mr Moscovici to discuss the economic impact of Brexit on Britain and the EU, before talking to Mr Barnier about the current progress of the divorce negotiations.
A Commission spokesman explained the get-together by saying its chief negotiators’ door is “always open” for people from “across the political spectrum and from all walks of life, all parties”.
The trio referred to themselves as “the rebels” as they arrived at the Commission’s headquarters for the meeting, with Mr Clarke joking: “We are talking about cricket.”
Their visit comes just 10 days after the Labour leader Jeremy Corbyn gatecrashed the last EU Council summit by travelling to Brussels for a meeting with Mr Barnier.
That get-together prompted a furious response from eurosceptics who accused the veteran socialist of “helping the EU, not Britain” by allowing it to muddy the waters in the negotiations.
However, whilst Mr Corbyn is at least the leader of the official opposition, and so could become the next Prime Minister, Mr Clarke is a backbencher and Lord Adonis a peripheral peer, whilst Mr Clegg is not even an MP any more.
A Brussels source said: “I imagine Barnier and co enjoy it because they are able to pick up soundings on the ground for how it’s going.”
EU Commission deputy chief spokesman Alexander Winterstein said: “His door is always open for people who want to speak to him and his team across the political spectrum and from all walks of life all walks of parties.
“There is a negotiating process. On one side is David Davis and on the European side is the chief negotiator of the EU Michel Barnier, nobody else.”
Asked who requested the meetings, he added: “All of these meetings were requested by the people who are coming to see Mr Barnier, that’s why I said his door is always open.
“There’s one single person negotiating for the 27 member states and the EU and that’s the chief negotiator Michel Barnier.”