Judges at London's High Court have thrown out an attempt to prosecute Boris Johnson, the frontrunner to succeed Theresa May as prime minister, for allegedly lying about Brexit during the 2016 EU referendum campaign.

Key points: Boris Johnson claimed the UK would be 350 million pounds a week better off outside the EU

Boris Johnson claimed the UK would be 350 million pounds a week better off outside the EU Mr Johnson's lawyer said the accuracy of the claim was still being debated

Mr Johnson's lawyer said the accuracy of the claim was still being debated The judges will reveal their reasons for the decision at a later date

The case revolved around a claim famously emblazoned on Johnson's 'Leave' campaign bus that Britain would be 350 million British pounds ($637 million) a week better off outside the European Union.

Opponents argued that it was deliberately misleading and it became symbolic of the divisions caused by the referendum, which saw Britons vote 52 to 48 per cent to leave the EU.

Marcus Ball, 29, had tried to prosecute Mr Johnson for misconduct in a public office and last month, a judge said Mr Johnson must appear in court over the allegation.

But at a judicial review hearing on Friday at the High Court, Mr Johnson's lawyer Adrian Darbishire said that judge had either erred in law or provided the wrong legal test in allowing the case to go ahead.

Mr Darbishire said the only rational conclusion was that the case was politically motivated and therefore vexatious.

"For the avoidance of doubt, it is denied by the claimant that he acted in any way improperly or dishonestly. Public debate about the accuracy or otherwise of the 350 million pounds continues to this day," Mr Johnson's lawyers said in a court document.

The High Court judges said they would give the reasons for throwing out the case at a later date.

Mr Ball said he was considering whether to appeal and would wait to see the judgement.

I will not give up until I believe that all possible options are exhausted," Mr Ball said.

A former Foreign Secretary, Mr Johnson is the front-runner among conservative lawmakers hoping to replace Ms May as party leader and therefore prime minister. He was not in court for the hearing.

Friday was Ms May's last day as leader, although she will remain prime minister until a successor is selected.

Reuters