Boris Johnson has been summoned to court to face accusations of misconduct in public office over claims that he lied by saying Britain gave £350m a week to the European Union.

The ruling follows a crowdfunded move to launch a private prosecution of the MP, who is the frontrunner in the Tory leadership contest.

Johnson lied and engaged in criminal conduct when he repeatedly claimed during the 2016 EU referendum campaign that the UK handed over the sum to Brussels, Westminster magistrates court was told last week by lawyers for a 29-year-old campaigner who has launched the prosecution bid.

District judge Margot Coleman ruled on Wednesday: “The allegations which have been made are unproven accusations and I do not make any findings of fact. Having considered all the relevant factors I am satisfied that this is a proper case to issue the summons as requested for the three offences as drafted. The charges are indictable only.

“This means the proposed defendant will be required to attend this court for a preliminary hearing, and the case will then be sent to the crown court for trial. The charges can only be dealt with in the crown court.”

The attempted prosecution is being brought by Marcus Ball, who has accused the former foreign secretary of misconduct in public office and raised more than £200,000 to hire a legal team.

The next hearing at Westminster magistrates court is expected to take place in three or four weeks and will be purely administrative, but Johnson will have to attend. He and his legal team will be asked if he intends to contest the case.

It would then be sent to a crown court, probably Southwark, where it would be listed for a preliminary hearing. At this point, Johnson’s team would be expected to seek to have the case dismissed.

A full trial, in front of a jury, would not be expected to take place for another six months, by which time Johnson could be prime minister.

The offence of misconduct in public office carries a maximum sentence of life imprisonment.

Acting for Johnson, Adrian Darbishire QC, told the court last week that the application by Ball had been brought for political purposes and was a “political stunt”.

“Its true purpose is not that it should succeed, but that it should be made at all. And made with as much public fanfare as the prosecution can engender,” he said. “The application represents an attempt, for the first time in English legal history, to employ the criminal law to regulate the content and quality of political debate. That is self-evidently not the function of the criminal law.”

However, in her ruling , the judge said she was satisfied there was a prima facie case for the allegation that there had been an abuse of the public’s trust in a holder of office.

She referred to statements provided by Ball’s team from members of the public that addressed the impact that “the apparent lie” had had on them. She also cited the contention by Lewis Power QC, counsel for Ball, that “there will seldom be a more serious misconduct allegation against a member of parliament or mayor than to lie repeatedly to the voting public on a national and international platform, in order to win your desired outcome”.

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, was also said to have informed the mayor’s staff that it was “official mayoral policy” to support the case for leaving the EU.

“A policy being deemed official, and therefore of the office, would make any campaigning thereafter by the proposed defendant official and pursuant to his office,” the ruling stated.

There was no immediate reaction from Johnson but a source close to the MP said: “This prosecution is nothing less than a politically motivated attempt to reverse Brexit and crush the will of the people.”

The ruling was also criticised by fellow pro-Brexit Tories, including David Davies, who said it was “deeply sinister” that Johnson faced being “dragged” into court. He added on Twitter: “EU supporters falsely claimed that a leave vote would collapse the economy. No action being taken against them.”