An ex-KGB chief suspected of helping the former MI6 spy Christopher Steele to compile his dossier on Donald Trump may have been murdered by the Kremlin and his death covered up. it has been claimed.

Oleg Erovinkin, a former general in the KGB and its successor the FSB, was found dead in the back of his car in Moscow on Boxing Day in mysterious circumstances.

Erovinkin was a key aide to Igor Sechin, a former deputy prime minister and now head of Rosneft, the state-owned oil company, who is repeatedly named in the dossier.