LONDON—Boris Johnson, the front-runner to replace Prime Minister Theresa May of Britain, was ordered Wednesday to appear in court for a preliminary hearing over allegations that he lied to the public during the 2016 Brexit referendum.

A judge ruled that Johnson, a former foreign secretary under May, must appear on a private summons to address three counts of misconduct in public office over several claims, including the suggestion that Britain paid £350 million ($440 million) every week to the European Union for the country’s membership.

The £350 million figure was a central theme of the pro-Brexit campaign, which promised to invest that amount into the nation’s health service should Britain vote to leave the bloc. The slogan was emblazoned on a Brexit campaign bus: “We send the EU £350M a week: let’s fund our NHS instead,” referring to the National Health Service.

But after Britons voted to leave the bloc by 52 per cent to 48 per cent, many supporters of Brexit abandoned the pledge, saying it had been a “mistake.” But opponents of Brexit argued that the campaign slogan had been a gross misuse of official statistics to deliberately misled voters.

The figure does not account for Britain’s rebate, which is deducted before it sends money to Brussels. Britain’s weekly net contribution to the EU in April 2016 was about £190 million, according to the Office for National Statistics.

Johnson, one of the most prominent voices in favour of leaving the EU, resigned as foreign secretary in 2018 in protest over May’s Brexit plan.

No one from Johnson’s office could immediately be reached for comment Wednesday. But he has denied wrongdoing, and his lawyers have argued that the case is a political stunt by opponents of Brexit.

Johnson, one of Britain’s most divisive politicians, is the favourite candidate in the contest to succeed May when she steps down as prime minister next week, according to bookmakers.

A victory for him could increase the chances of Britain’s leaving the EU without a deal in October, which could potentially have dire economic consequences.

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