LONDON, April 17 -- UK Prime Minister Keir Starmer said Friday he was "furious" after it emerged his sacked US ambassador Peter Mandelson was appointed despite failing security vetting, as the scandal again threatens his hold on power.

The beleaguered British leader, who has been dogged for months by the controversy, claimed he and other ministers were not told Mandelson had failed the vetting process, branding that "unforgivable".

Starmer has faced repeated calls to quit since his 2024 decision to appoint Mandelson as Britain's top diplomat in Washington backfired spectacularly over the envoy's longstanding ties to late US sex offender Jeffrey Epstein.

Starmer sacked Mandelson in September, just seven months after taking up his post....