A legal challenge by a group of British expats who want to halt Brexit because of “corrupt and illegal practices” by pro-Leave organisations has reached the High Court.

The UK in EU Challenge group says the Prime Minister’s decision to trigger Article 50, the mechanism by which the UK will leave the EU, should be quashed because of “misconduct” by campaigners in the run up to the 2016 referendum.

Vote Leave was fined £61,000 and referred to the police while Leave.EU was fined £70,000 following investigations by the Electoral Commission.

The group will argue these electoral offences render both the result of the referendum, and the notification to leave the EU under Article 50, void.

Their lawyers will ask Justice Ouseley to grant permission for a full judicial review at a hearing in London.

The judge will also be asked to consider research by Professor Philip Howard, director of the Oxford Internet Institute, who has concluded Vote Leave reached tens of millions of people in the days before the historic vote – after breaching its spending limits.

Carole-Anne Richards, one of the UK in EU Challenge claimants, said: “Members of the public should be able to rely on the fact that the process behind any vote, not least one so far-reaching for the UK, is carried out lawfully, free from corrupt and illegal practices.

“This is clearly not the case here.

“We are very grateful to Professor Howard for his work in looking at Vote Leave Facebook advertising overspend and correlating that with voter behaviour.

“Anything that sheds light on what took place, especially where illegalities have been proven, is to be welcomed and should be made available in the public interest.”

Rupert Croft of Croft Solicitors, representing the group, said: “The claimants contend that it’s essential that Parliament understands the legal and constitutional status of the result of the referendum.

“The serious breaches of electoral law that have recently come to light have cast doubt on the legitimacy on the referendum result.

“Parliament is entitled to have the guidance of the court as to the correct legal position. This case should enable that.”

The case is being brought against the Prime Minister Theresa May, whose lawyers will urge the court to reject it.