May warned against becoming '˜unwitting tool of aggressive nationalism' ahead of Trump meeting

The stark words from the former deputy Prime Minister Nick Clegg come as the Labour Party comes under increasing pressure to clarify its stance on Article 50 ahead of today’s Supreme Court ruling.

Mrs May is due to meet with President Trump on Friday, with a post-Brexit trade deal between the US and UK expected to be at the top of the agenda.

Speaking at a conference in Brussels today, Mr Clegg will argue that President Trump and the Russian premier Valdimir Putin are effectively colluding to weaken Europe’s security and prosperity – and Mrs May runs the risk of becoming their “unwitting tool”.

“Theresa May’s approach to Brexit is not only contrary to Britain’s national interest, it also runs the risk that the Brexit negotiations unwittingly become the means by which the forces of aggressive nationalism seek to unpick the EU itself,” he will say.

“This has long been the stated ambition of the most hardline Brexiteers, and was repeated at the meeting of populist parties held in Koblenz this weekend.

“Her vision for a hard Brexit will pull us out of the European Single Market, the world’s largest borderless marketplace – which was, let’s not forget, designed by the British and championed by the Conservative Prime Minister at the time, Margaret Thatcher.

“That is the wrong choice for Britain’s interests.”

The address comes as MPs await the Supreme Court ruling on whether Parliament should have a vote on triggering Article 50.

The Labour leadership is coming under growing pressure to state whether or not it will support legislation, amid reports that dozens of Labour MPs are concerned about the consequences of a “hard” Brexit.

Several MPs have told this paper that they want to see the Bill before they decide whether they will back it, or seek to amend or even block it.