The UK parliament must first debate and vote on whether to trigger Article 50, starting a two-year process to leave the European Union, London lawyers Mishcon de Reya said on Sunday.

Acting a behalf of a group of clients, the firm said it would challenge the government in court if it proceeded to leave the EU without first getting permission from parliament.

Recognizing a majority of UK voters expressed a desire to leave the 28-member bloc, the law firm said the referendum was not legally binding and was meant as an "exercise to obtain the views of UK citizens."

Referendum among other factors

"But the decision to trigger Article 50 of the Treaty of European Union, the legal process for withdrawal from the EU, rests with the representatives of the people under the UK Constitution," the law firm said in a statement on Sunday.

"If the correct constitutional process of parliamentary scrutiny and approval is not followed then the notice to withdraw from the EU would be unlawful, negatively impacting the withdrawal negotiations and our future political and economic relationships with the EU and its 27 Member States, and open to legal challenge," the firm said.

"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," Kasra Nouroozi, a partner at Mishcon de Reya said.

Britain does not have a codified constitution but an unwritten one formed of Acts of Parliament, court judgments and conventions. This adds further questions about the constitutional process for an exit from the EU.

Demonstrations against leaving the EU in London

Rudderless

The surprise June 23 Brexit vote outcome has catapulted Europe and the UK into uncharted territory, with all sides scrambling on how to navigate through a turbulent and uncertain period. In the UK, lawmakers for and against leaving in the EU are at odds over how to negotiate an exit, and when to start the process to leave.

On the continent, European leaders are pushing for the UK not to drag out implementing Article 50 for too long over concern a long delay adds uncertainty and could roil financial markets.

A legal challenge could throw any departure date into further uncertainty, and if accepted by the court, could bog down an exit. Scotland, meanwhile, has indicated its parliament may take measures to try to block a Brexit, or hold a second referendum on leaving the UK altogether so it can remain in the EU.

cw/jm (AFP)