Andrei Lugovoy, also a former spy, said he holds evidence that MI6 had a hand in Litvinenko’s poisoning by polonium-210. He also said MI6 tried to recruit him to collect information on President Putin and that both Litvinenko and exiled tycoon Boris Berezovsky were in its pay.

Lugovoy told a news conference in Moscow: “Even if (British special services) hadn’t done it itself, it was done under its control or connivance.”

The startling allegations are the latest twist in the hunt to bring whoever murdered Litvinenko in London last November to justice.

Papers calling for Lugovoy’s extradition were formally submitted to the Russian authorities earlier this week. The Crown Prosecution Service charged the Russian businessman with murder following an exhaustive investigation by detectives at Scotland Yard.

But the Russians said they will not extradite Lugovoy as it would breach their constitution.

Lugovoy made a number of claims during a press conference, translated by the Russia Today television channel. He said British special services “asked me to collect compromising information on President Putin”. And he claimed Litvinenko and his billionaire friend Berezovsky, now wanted in Russia, were working for British intelligence.

Lugovoy worked for the KGB and its main successor agency the FSB. He is now a successful businessman training bodyguards.

He and another Russian met in London with Litvinenko on November 1, the day Mr Litvinenko said he became ill. Police later found traces of the rare isotope polonium-210 at a number of locations including hotels, a restaurant and aeroplanes, used by Lugovoy.

Litvinenko later died in University College Hospital, after recording a message on his death bed accusing Mr Putin of being behind the poisoning.

© Copyright Press Association Ltd 2007, All Rights Reserved.