No minister was told that Mandelson's security clearance had failed, Starmer says, calling it "inexcusable".
The move comes after Olly Robbins, the most senior official at the British Foreign Office, was forced out following The Guardian's revelation that Mandelson became Britain's ambassador to the US without a proper vetting process.
The opposition is also demanding that Starmer resign.
"It's time for him to take responsibility," writes Tory leader Kemi Badenoch on X.
"Heads must be rolling," writes former Home Secretary and Foreign Secretary James Cleverly.
Mandelson was fired when his close contacts with convicted sex offender Jeffrey Epstein were revealed last year.
