An attempt to prosecute Boris Johnson over the claim that Britain gave the EU £350m a week has been thrown out by a judge.
Marcus Ball, a 29-year-old entrepreneur who has so far raised £570,000 for the case, had sought permission to appeal to the Supreme Court.
But the bid was refused by Lady Justice Rafferty on Wednesday.
“This application for leave to appeal to the Supreme Court is rejected,” the High Court judge said.
Mr Ball said his legal team were considering options including appealing directly to the Supreme Court or taking the case to the European courts.
“This isn’t over, we are not giving up,” he added. “We are pursuing it, absolutely.”
A judge initially summonsed Mr Johnson to appear at Westminster Magistrates’ Court over accusations of misconduct in public office in May, but the Divisional Court overturned the ruling in June.
At a hearing in July, Mr Ball’s lawyers filed an application challenging the Divisional Court’s decision to quash the summons for Mr Johnson.
They argued that judges were wrong to find that misconduct in public office laws could not be used for political campaign statements.
Mr Ball said the case “goes to the heart of the UK’s democratic process and public”.
“It is worrying and highly damaging to society that our courts have seemingly sanctioned the misuse of status, opportunity and influence,” he added after Wednesday’s hearing. “It is a green light for all public office holders to lie.”
The figure was emblazoned on the red campaign bus during the 2016 EU referendum, with the slogan: “We send the EU £350m a week, let’s fund our NHS instead.”
Mr Johnson’s lawyer said his client – who was the mayor of London and a backbench MP during the period - denied acting dishonestly and argued Vote Leave’s £350m-a-week claim was based on information that was “freely available to all”.
Adrian Darbishire QC said the district judge who summonsed the former foreign secretary to court had “erred in law”.
“It was just a political claim open to and available for contradiction and debate, and it was, and is, for the good sense of the electorate to discount it if they choose so to do,” the lawyer added.
“It is not for the Crown Prosecution Service, judge and jury to determine the misconduct of this claim and it is not for the interested party either.”
In a full ruling published in July, High Court judges concluded that the “problem of false statements in the course of political campaigning is not new”.
Lady Justice Rafferty and Mr Justice Supperstone said laws governing the issue did not cover arguments used in political campaigns like the EU referendum.
“There is no precedent for any office holder being prosecuted for misconduct in public office for wilfully making or endorsing a misleading statement in and for the purposes of political campaigning,” their ruling said.
The judges said that allegations that Mr Johnson knew Vote Leave’s £350m-a-week claim was false would not amount to neglect of duties or the abuse of state power.
They noted a 2016 Electoral Commission report, which predicted that opposing sides of the Brexit debate would contest each other’s claims but said it was the “role of campaigners to debate the relative merits of their arguments”.
Mr Johnson’s lawyers had also claimed the case was “motivated by a political objective” to undermine the result of the EU referendum.
High Court judges said Mr Ball had deleted large parts of his social media history but a previous crowdfunding website post discussed legal options to “prevent Brexit”, and he had called himself “pro-Remain”.
“We would also have quashed the decision on the basis that the finding that the prosecution was not vexatious was flawed,” they concluded.