Britain cannot leave the European Union without a vote in parliament, Government lawyers have said.
Although the prime minister could trigger the two-year process of negotiating the UK's withdrawal without a formal Act of Parliament, MPs would have to vote to repeal legislation relating to the EU.
Oliver Letwin, the Cabinet minister in charge of leaving the EU, has said the legal advice is that Article 50 of the Lisbon Treaty can be invoked without parliamentary approval under the royal prerogative, The Guardian reports.
Once triggered, Article 50 will begin the process of Britain leaving the EU.
However, MPs would have to vote to repeal the European Communities Act 1972 through an Act of Parliament.
According to The Guardian, leading constitutional lawyers say the French government legal service has told the French government that the UK would be entitled to rescind its notice to withdraw even after it invoked Article 50.
This suggests the UK could reverse its decision to withdraw through a vote in parliament or a second referendum.
A second EU referendum would be possible if it becomes clear public opinion has shifted strongly against Brexit, the former attorney general has said.
Dominic Grieve, a Conservative MP who was the Government’s chief legal advisor until 2014, said the result of the first referendum had to be “treated with respect” but that it was not necessarily set in stone.
Mr Letwin has also defended the Government's policy of doing absolutely no contingency planning for Brexit ahead of the referendum.
The Cabinet minister told the Foreign Affairs committee on Tuesday it would not have been possible to do significant planning before the vote took place.
Britain voted to leave the European Union by 52 per cent to 48 per cent, prompting David Cameron to announce his resignation.
The Prime Minister said it would be for his successor - chosen by the Conservative Party - to deal with the specifics of how Britain would leave the bloc.
