Senior US officials believed Russian prime minister Vladimir Putin may well have known about the murder of spy Alexander Litvinenko (AP)

The British government has ordered potentially vital information about whether murdered former Russian spy Alexander Litvinenko had links with the UK intelligence services to be withheld from his inquest.

Scotland Yard investigated claims that Mr Litvinenko, who was poisoned with radioactive Polonium 210 in 2006, was in regular contact with MI6 or MI5 prior to his death as part of an inquiry which led to murder charges against two Russian citizens – both former KGB agents.

But a preliminary hearing for the long-delayed inquest into Mr Litvinenko's death, due to start in the new year, heard that Whitehall officials have asked for the findings relating to the intelligence agencies to be removed from the information due to be made public during the hearings.

The attempt to shroud any dealings with the former Russian agent in secrecy was disclosed as Mr Litvinenko's widow, Marina, said she wanted the proceedings to establish once and for all whether her husband was the victim of a "targeted assassination" on British soil by a foreign state.

The audacious killing of Mr Litvinenko, 43, who was poisoned in a Mayfair hotel, plunged relations between London and Moscow into their deepest freeze since the Cold War. The inquest is likely to renew tensions between the two countries at a time when both sides have been inching towards a new diplomatic detente.

Moscow has consistently refused requests for the extradition of prime suspect Andrei Lugovoi, a former KGB agent turned businessman who was elected a Russian MP. Mr Lugovoi, who is represented in the inquest proceedings, denies all involvement in Mr Litvinenko's death.

Lawyers for Mrs Litvinenko, who attended yesterday's hearing with the couple's son, Anatoly, said she and others believed the Russian state was responsible for her husband's death.

Ben Emmerson QC said: "If that hypothesis were to be evidentially substantiated, this would be an act of state-sponsored nuclear terrorism on the streets of London." A report by the Metropolitan Police summarising the findings of its investigations, including the question of whether Mr Litvinenko was assisting British intelligence, is due to be submitted to the inquest and interested parties within the next fortnight.

The hearing was told that the Government has ordered that findings relating to Mr Litvinenko's alleged relationship with MI5 or MI6 have been shown to the coroner, High Court judge Sir Robert Owen, and his team but cannot be made public or shown to interested parties such as Mrs Litvinenko or Mr Lugovoi.

Once the report is submitted, Sir Robert can decide whether the redactions should remain. Any attempt to pull a permanent veil over whether Mr Litvinenko, an outspoken critic of Russian president Vladimir Putin, had been in contact with British agents is likely to give rise to criticism of excessive secrecy. Following his death, it was reported that Mr Litvinenko had co-operated with British intelligence as part of the battle against organised crime from Russia and eastern Europe and may have been receiving a monthly retainer of £2,000.

Hugh Davies, counsel for the inquest, said that the redactions on behalf of the Government did not amount to an admission that Mr Litvinenko was working for the British security services and insisted all competing theories about the killing would be examined at the inquest. He added: "The court is committed to transparency."

The Yard investigation concluded that Mr Litvinenko was poisoned with the polonium while drinking tea at a meeting, allegedly with Mr Lugovoi and another former KGB agent, Dmitry Kovtun, at the Millennium Hotel in Mayfair. Mr Emmerson said: "It is Mrs Litvinenko's firm position that this inquiry should be capable of investigating and determining whether her husband's killing was a targeted assassination of a British citizen carried out by agents of a foreign state in the sovereign territory of the United Kingdom."

Sir Robert signalled that he intended to allow the inquest to follow all relevant lines of inquiry, saying he endorsed a previous ruling in the case by Dr Andrew Reid, the St Pancras coroner.

In the ruling, released yesterday, Dr Reid said: "If Mr Litvinenko is shown to have died as a result of ingestion of Polonium 210 the public interest plainly demands and open and fearless investigation into the full circumstances, including how and why this fatal ingestion occurred. Any lesser level of inquiry would not command public confidence either nationally or internationally."

Belfast Telegraph