British citizens living in other EU countries have launched a court challenge against Brexit on the basis of electoral law breaches during the referendum campaign.

The UK in EU Challenge group, represented by English law firm Croft Solicitors, argues that the referendum was not conducted “in accordance with the UK’s constitutional requirements”.

The statement of facts filed with the High Court in London states that the referendum result is “vitiated by corrupt and illegal practices, and the basis of the decision made by Prime Minister thereby fundamentally undermined”.

It adds: “Neither the decision nor notification under Article 50 was in accordance with the UK’s constitutional requirements.”

The UK government argues that the application for judicial review is “substantially out of time” and too similar to R (Webster) v Secretary of State for Exiting the EU [2018] EWHC 1543, which was rejected.

However, lawyers for the UK in EU Challenge group say that it is not out of time because the Electoral Commission only identified breaches of electoral law by the pro-Brexit Vote Leave campaign in July.

Rupert Croft, managing director at Croft Solicitors, told The Guardian: “Our clients contend that the prime minister’s decision to trigger article 50 and start the Brexit process was based on a factual error, namely that the referendum truly represented the will of the people following a lawful, free and fair vote.

“They argue that the decision to trigger article 50 to withdraw from the EU was therefore not in accordance with the UK’s constitutional requirements. We look forward to having this important constitutional case considered by the court.”