The case against Boris Johnson has collapsed – but key Leave figures still face criminal sanctions

The prosecution of Boris Johnson on charges of misconduct in public office over the Leave campaign may have been overturned – but legal bids to challenge the claims made in the run-up to the Brexit referendum do not end there.

High Court judges explained on Wednesday why the Tory leadership hopeful would not face court over his widely discredited pledge to funnel £350m a week from the EU to the NHS.

Lady Justice Rafferty and Mr Justice Supperstone said false claims in politics were “not new”, but there was no precedent for action on statements made during campaigns.

However, there have been attempts elsewhere to seek recourse over alleged wrongdoing by the Leave campaign, which has been rumbling on since 2016.

Vote Leave, the official campaign, has been at the centre of a row over campaign financing, which is governed by strict rules to prevent wealthy parties from outgunning smaller campaign groups.

Last year, it was fined £61,000 and referred to the police by the Electoral Commission for breaches of spending limits during the campaign.

The elections watchdog said Vote Leave had exceeded the £7m spending limit by making a £675,000 payment to youth group BeLeave, run by student Darren Grimes.

The Electoral Commission said it found “significant evidence” of joint working by the campaign groups. Mr Grimes was also fined £20,000 and referred to the police.

Vote Leave has always denied any wrongdoing and says the complaints are politically motivated.

Leave.EU was also fined after it was found to have exceeded its spending limit. As it was not the official campaign, the group, backed by Nigel Farage and funded by Arron Banks, had a limit of only £70,000, compared with Vote Leave’s £7m.

Mr Banks called the findings “a joke” and said it was an attempt to undermine the referendum result.

The National Crime Agency (NCA), meanwhile, has launched a separate probe into a number of suspected offences committed by Mr Banks and Elizabeth Bilney, chief executive of Leave.EU.

The Metropolitan Police has received more than 2,000 documents from the Electoral Commission but no announcement has yet been made on any potential criminal charges.

Last month, a cross-party group of MPs sent a legal letter to the Met demanding an explanation over delays ​and warning they will seek judicial review if no action is taken. The timeframe for the demands is being resisted by the police.