A former Conservative lawmaker and 14 others have been charged with cheating when placing bets on the timing of Britain’s general election last year, the Gambling Commission said Monday.

Craig Williams was one of several people who had been investigated for cashing in on insider knowledge on the date then-Prime Minister Rishi Sunak would call the election. Other members of the Conservative Party that controlled government at the time and a police officer were among those facing chares that…