A British judge has ruled that former Foreign Secretary Boris Johnson will be summoned to court to answer questions about his possible misconduct in public office during the Brexit referendum campaign in 2016.

District Judge Margot Coleman said Wednesday that Johnson will be questioned about whether he lied during the campaign when he said Britain contributed 350 million pounds ($442 million) to the European Union each week.

Lawyers representing an individual pursuing a private prosecution of Johnson asked Westminster Magistrates’ Court to summon the politician.

The judge said the allegations against Johnson are “unproven” but added that issuing a summons is proper.

Johnson is a prominent contender in the Conservative Party leadership race who stands to become prime minister if he wins that contest.