London —

Wes Streeting has resigned as Britain’s health secretary, saying Thursday that he has “lost confidence” in Prime Minister Keir Starmer’s leadership and that it would be “dishonourable and unprincipled” to remain in his government.

The move comes after days of speculation about whether Streeting would formally challenge Starmer’s leadership of the Labour Party. In his letter to the prime minister, Streeting announced his resignation from government, but did not say that he was launching a leadership contest.

In order to trigger that contest, Streeting needs to gain the support of one fifth of Labour’s members of parliament (MPs) – at present, 81 lawmakers.

In the wake of Streeting’s resignation, Starmer appointed James Murray, former chief secretary to the treasury, as the new health secretary.