THERESA May has caused more bad feeling in Brussels by declining to address MEPs on Britain’s withdrawal from the European Union.

Her refusal came as the European Commission warned the negotiations were at risk of failure after it questioned Brexit Secretary David Davis’s “stability and accountability".

At Westminster, MPs engaged in the first of two days of debate on the UK Government’s flagship Repeal Bill with senior Conservative Dominic Grieve, the former Attorney General, pointing to a possible Tory rebellion ahead.

While the Government is expected to win Monday’s vote on the bill’s Second Reading, Mr Grieve told MPs the legislation was “in many respects an astonishing monstrosity” and that, if it were not substantially improved, he would vote against it in the final key Commons vote.

In a sign of Tory divisions, dozens of Brexit-supporting Conservative MPs signed a letter, cautioning ministers against using a post-withdrawal transitional period to stay in the EU "by stealth".

No 10 confirmed that Mrs May had received an invitation to the European Parliament by its President, Antonio Tajani, and that she would address a private meeting of EU leaders.

But Brussels sources claimed the PM had turned down an invitation to address MEPs, which would have meant her following in the footsteps of Margaret Thatcher, Tony Blair and Gordon Brown.

In response, German MEP Elmar Brok said: “Why make enemies? It’s ridiculous.” Nigel Farage, the Ukip MEP, said not addressing the full parliament, which will have to approve the final Brexit deal, would “be a mistake”. He added: “If she's going to come, she ought to address the full plenary."

Earlier, official EU documents showed Jean-Claude Juncker, the Commission President, had expressed concern over the “stability and accountability of the UK negotiator and his apparent lack of involvement, which risked jeopardising the success of the negotiations”.

A Commission spokeswoman refused to comment on the documents but insisted things had "moved on" since they were written in July.

Meanwhile, Alex Salmond, addressing the annual dinner of the pro-independence Business for Scotland organisation in Glasgow last night, was set to “extol the virtues” of membership of the European Free Trade Association.

This would mean a country might be out of the EU but would retain membership of the single market. The former First Minister was also expected to say that a Tory hard Brexit would make a second independence referendum “inevitable”.