An attempt to bring a private prosecution against Boris Johnson for allegedly telling lies during the 2016 referendum campaign appears to have been dealt a fatal blow with the rejection of an application to take the case to the supreme court.

High court judges threw the case out in June after Johnson challenged a summons to attend court on three claims of misconduct in public office.

Marcus Ball, 29, who raised more than £300,000 through online crowdfunding to bring a private prosecution and has been working on it for the past three years, said on Wednesday that it was “not over” and that he and his legal team were looking at further options.

The case made headlines when a district judge, Margot Coleman, issued Johnson, then a Conservative leadership hopeful, with a summons on 29 May to attend Westminster magistrates court and face three allegations of misconduct in public office.

But after a hearing at the Royal Courts of Justice on 7 June, Lady Justice Rafferty and Mr Justice Supperstone overturned the decision.

In a written judgment, the court said the crime of misconduct in public office was about “neglect of duties or abuse of state power”. It said: “No authority was shown to us suggesting that the offence can be or has been equated to bringing an office into disrepute or misusing a platform outside the scope of the office.”

Speaking outside the high court on Wednesday after a hearing in which Rafferty refused an application to appeal to the supreme court, Ball insisted he would fight on.

“We have several options which we are now looking at,” he said

“One is to appeal to the European courts because what the UK courts system is essentially saying is that Boris Johnson is above the law. What choice do we have?

“Forget Boris Johnson for a moment. The ruling in this case applies to all public officers. It applies to army generals, judges and others. They can go on national television and lie to millions of people without any consequences.”

Ball added that other options could include seeking to go directly to the supreme court and seek a reason for why the appeal cannot be brought forward.

Ball said that he was now in a grave financial situation and estimated that he owed as much as £200,000. Members of the public had shown goodwill in funding his case, he added, but he hoped that those who continued to support him in the future would do so out of belief in the case.

Ball’s lawyers told Westminster magistrates court earlier this year that Johnson lied and engaged in criminal conduct when he repeatedly claimed during the 2016 referendum campaign that the UK handed over £350m a week to the European Union.

A central plank of the case put forward by Ball’s team was that Johnson, as an MP and previous mayor of London, “lied and misled” the public about the cost of EU membership and used the “platforms and opportunities offered to him by virtue of his public office”.

Coleman’s ruling noted that, as mayor, Johnson signed off several letters in that capacity when expressing his views on Brexit. His then chief of staff, Edward Lister, who is now the prime minister’s strategic adviser, was also said to have informed the mayor’s staff that it was “official mayoral policy” to support the case for leaving the EU.