Law firm Mishcon de Reya has been instructed to launch a legal challenge to block Britain from leaving the European Union, in spite of the popular vote to leave the bloc.

Solicitors and barristers from Mishcon de Reya are working with Blackstone, Matrix and Monckton Chambers to argue Article 50 of the European Union – the legal process of withdrawing from the EU – can only be triggered after a vote in Parliament.

Mishcon de Reya said “legal steps have been taken” to ensure Article 50 will not be triggered without an Act of Parliament.

Triggering Article 50 without consent of Parliament would be unlawful, the firm alleged. In a statement, it said:

The Referendum held on 23 June was an exercise to obtain the views of UK citizens, the majority of whom expressed a desire to leave the EU. 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.

Mishcon de Reya did not say on whose behalf it is acting, but the Financial Times indicated it was “on behalf of a group of businesses.”

Neither did it say what legal steps have been taken or who has been targeted. The suggestion is that the defendant in the case would be the government, as the lawyers lining up have considerable pedigree in taking on EU law and UK regulators alike.

Mishcon de Reya's clients include UK outsourcing giant Capita Group, Dell, Hewlett Packard and Microsoft. At this stage there is no indication that those firms have instructed lawyers to sue the government and have the referendum decision disregarded.

Microsoft, however, was a vocal supporter of Remain.

Matrix is currently representing BT against Ofcom and has a history of cases in telecoms and European regulation. Monckton’s clients include BT, Orange Telecom and Ryanair – the low-cost airline that campaigned against Brexit.

The intervention comes at a critical time in the maelstrom that is British politics at present.

The ruling Conservative Party is embroiled in a campaign to select a new leader, and thus the country’s next Prime Minister.

Contenders, and Leave advocates, Andrea Leadsom and Liam Fox have vowed to trigger Article 50 as soon as they are elected party leader and become PM.

Remain candidate Theresa May, viewed as the front runner, has said the UK must organize a formal negotiating position first and that a formal Article 50 notice would not be given until the end of the year.

Prime minister David Cameron announced, on the morning of the referendum result, that he would resign by the date of Conservative Party conference in October. ®