Sir Keir Starmer was warned about the "reputational risks" posed by Lord Mandelson's ties with Jeffrey Epstein before he confirmed his appointment as US ambassador.
On Wednesday, the government was forced to release the first batch of internal documents related to Lord Mandelson's appointment as US ambassador.
The documents, the BBC reports, include details of advice given to the prime minister outlining that Mandelson's relationship with Epstein continued after the latter's conviction for an offence relating to an underage girl in 2008.
A total of 147 pages of documents have been released so far, with more to follow.
Darren Jones, Starmer's chief secretary, said the due diligence process "fell short" in relation to Mandelson, and that the government had since made changes to correct "weaknesses in the system".
The documents released so far also include disputed discussions around Mandelson's severence package when he was sacked last September.