A law firm has launched a legal challenge to ensure the process for Britain leaving the European Union does not begin without a parliamentary debate and a vote.

Lawyers at Mishcon de Reya claim the Government cannot trigger Article 50 without an act of Parliament.

The firm said in a statement that a "group of clients" is behind the legal action, but did not name them.

It claimed it has been in talks with Government lawyers since 27 June, four days after the Leave campaign triumphed in the EU referendum.

In order for the UK to leave the EU, the Government must invoke Article 50, after which time Britain has two years to negotiate the terms of exiting the bloc.

But Mishcon de Reya argues "the outcome of the referendum itself is not legally binding and for the current or future prime minister to invoke Article 50 without the approval of parliament is unlawful".

Kasra Nouroozi, a partner at the firm, said: "We must ensure that the Government follows the correct process to have legal certainty and protect the UK Constitution and the sovereignty of parliament in these unprecedented circumstances.

"We must make sure this is done properly for the benefit of all UK citizens.

"Article 50 simply cannot be invoked without a full debate and vote in Parliament.

"Everyone in Britain needs the Government to apply the correct constitutional process and allow Parliament to fulfil its democratic duty which is to take into account the results of the referendum along with other factors and make the ultimate decision."