Theresa May has announced that the UK will still be joined by the rulings of the European Court of Justice during a transition period after Brexit, causing a backlash from eurosceptic Tory MPs.

In an interview with Newsnight, Jacob Rees-Mogg said: “We cannot be a colony of the EU for two years from 2019 to 2021, accepting new laws that are made without any say so of the British people or Parliament or Government.”

He went on to add: “That is not leaving the EU, that is being a vassal state of the EU and I would be very surprised if that is Government policy.”

The Brexiteer said: “I am always applauding Mrs May, I think she is an excellent Prime Minister, giving clear leadership over Brexit.”

However, he said “the British Government would be very unwise to accept” the EU’s intention that “in the transition period we will be bound by the single market, the European Court and the acquis.”

Negotiating guidelines for the second phase of the Brexit talks published by the European Council state that “all existing European structures” including the “competence” of the ECJ will apply to the UK throughout the two-year transition period.

This has forced Mrs May to suggest that the UK could have to accept new EU laws and regulations during the transition period.

Mr Rees-Mogg went on to say: “It has not been agreed as far as I am aware by the British Government and it would be a ridiculous situation to be in.”

“The Prime Minister has consistently said that she is in favour of an implementation which means we leave in March 2019 and that the consequences of leaving are implemented.

“The transition which the EU is offering means that we are effectively still in the EU for the following two years.”

Mr Rees-Mogg said: “Some of the criticism made of the strong pro-European’s has been unfair” and he does not think Tory rebels are “driving government policy.”

He said: “I think it is quite clear that we will leave” and that “the negotiations are moving towards that and we will be out of the single market and out of the customs union, which is tremendously important.”

This comes after the MP for North East Somerset hit out at the deal sealed to progress onto the second round of talks – arguing Britain needs to be “robust” if it wants to stand up to Brussels.

The Brexiteer hit out at the possibility the EU “acquis” – the sum of all EU law and legislation – could still apply to the UK after Brexit, as well as the rule of the ECJ and free movement.

He said: “As usual, the EU has set out a hard-nosed negotiating stance, we must be equally robust.

"If the acquis, the ECJ and free movement remain we would not be in an implementation period but would still be de facto in the EU.

“I assume that Her Majesty’s Government will make its own proposals and not roll over in the way it did at the beginning of the process.”

It comes after Mr Rees-Mogg was revealed to be Conservative Party members’ top choice for promotion to Theresa May’s Cabinet after winning a landslide victory in a recent poll.