British Defense Secretary John Healey unexpectedly resigned on Thursday, citing the government’s unwillingness to provide sufficient military funding amid “rising threats”. The resignation is yet another blow to embattled Prime Minister Keir Starmer, who is already facing calls from his Labour Party colleagues to step down.

In a letter to Healey, Starmer said he regretted his departure, but insisted that the funding plan would provide “sustainable and fair” spending growth, thereby ensuring the UK’s security.

Later on Thursday, the Prime Minister appointed former Security Minister Dan Jarvis as Defense Minister.

Stamer has pledged to increase the UK’s defense spending as a percentage of gross domestic product to 2.5% by 2027 and to 3% by 2035. However, many military officials say this is not fast enough.