Boris Johnson, the front-runner to become Britain's next prime minister, must attend court over allegations that he knowingly lied during the Brexit referendum campaign, a judge announced yesterday.

Johnson, the former foreign secretary, will be summoned to appear before a court over allegations of misconduct in public office, judge Margot Coleman said in a written decision, without specifying the date. The case is over the claim that Britain sends £350 million ($440 million) a week to the European Union. The exact amount of Britain's net and gross EU contributions was one of the biggest issues during the 2016 referendum campaign. Businessmen Marcus Ball has crowd-funded the private prosecution. Coleman's decision follows a hearing last week at Westminster Magistrates Court in London.

"The allegations which have been made are unproven and I do not make any findings of fact," the judge said. "Having considered all the relevant factors I am satisfied that this is a proper case to issue the summons as requested," she wrote. Referring to Johnson as the "proposed defendant," Coleman said he would be required to attend a preliminary hearing that could then result in a trial.

Johnson is considered the favorite among the 11 candidates vying to replace the outgoing Theresa May as leader of the governing Conservative Party and therefore prime minister, by the end of July. The maximum penalty for misconduct in public office is life imprisonment.