A leaked intelligence dossier compiled by the former MI6 Russia desk chief alleges Lord Mandelson was regarded as a “privileged contact” by Russian intelligence agencies for more than three decades.
The allegations, first reported by The Telegraph, are contained in a report codenamed Project Fish, which was compiled in 2022 by Christopher Steele.
It claims Moscow’s intelligence services viewed the Labour peer as “one of the most significant RIS (Russian intelligence services) achievements in manipulating UK politics” over the past 30 years.
The dossier does not provide evidence that Lord Mandelson knowingly worked for Russian intelligence or engaged in espionage.
Those close to the former Labour minister have dismissed the allegations as “nonsense”, insisting he never acted improperly on Russia’s behalf.
According to the report, the KGB first opened a file on Lord Mandelson while he served as Labour’s director of communications between 1985 and 1990.
It alleges he was first contacted by Soviet intelligence around 1990, shortly after the fall of the Berlin Wall, before later becoming what the dossier describes as a “privileged contact” for Russian intelligence.
The report says: “Sources claim that Mandelson is considered to be one of the most significant RIS achievements in manipulating UK politics over the last three decades.
The KGB opened its file on Mandelson in the Soviet era when he served as the Labour Party’s Director of Communications (1985-1990).
“He was contacted by the KGB for the first time in about 1990 and since then has become a privileged contact for Russian intelligence.”
The dossier alleges Russian intelligence continued monitoring Lord Mandelson’s rise through Tony Blair’s Government before later focusing on him during his tenure as European Union trade commissioner.
It also claims Russia’s foreign intelligence service, the SVR, compiled material relating to Lord Mandelson’s friendship with convicted sex offender Jeffrey Epstein that could potentially have been used as leverage.
The report further references Lord Mandelson’s former role on the board of Russian conglomerate Sistema, alleging it brought him into contact with intelligence operatives posing as business executives and government officials.
It also revisits allegations from 2008 concerning Lord Mandelson’s relationship with Russian oligarch Oleg Deripaska, which he has previously denied.
Lord Mandelson was appointed Britain’s ambassador to Washington in 2025 despite failing the highest level of security vetting over concerns relating to his connections with prominent Russian and Chinese figures.
Downing Street sources declined to tell the newspaper whether ministers had been made aware of the contents of Project Fish before his appointment.
Those close to Lord Mandelson rejected the dossier’s claims, saying he never supplied information to Russia or acted as an agent of influence.
They also pointed to his long record of publicly criticising the Kremlin, including opposing Russia’s seizure of Sistema’s energy assets, which they said resulted in his Russian visa being suspended for six months.
The Metropolitan Police is investigating Lord Mandelson over alleged leaks to Jeffrey Epstein during his time in Gordon Brown’s Government, while the European Union has also launched an inquiry into alleged fraud or serious misconduct during his tenure as trade commissioner.
Lord Mandelson has previously denied wrongdoing and has not been charged.
Project Fish was compiled by Mr Steele through his private intelligence firm, Orbis Business Intelligence, rather than in an official capacity.
The former MI6 Russia desk chief’s credibility has faced scrutiny since his controversial dossier on Donald Trump emerged in 2017, with critics questioning the methodology used to compile both reports.
