Tony Blair vowed today that "no diplomatic or political barrier" would be allowed to hamper the police investigation into the death of Alexander Litvinenko, the former Russian spy who died of radiation poisoning last week.

Speaking in Copenhagen, before he travelled to Riga for a Nato summit, the Prime Minister described the case as "very serious". If necessary, he said that he would take up the matter with President Vladimir Putin of Russia.

"I have not spoken to President Putin but I will do so at any time that is appropriate," said Mr Blair."There is no diplomatic or political barrier in the way of (the) investigation going wherever it needs to go."

He added: "It obviously is a very serious matter and we are determined to find out what happened and who is responsible."

Detectives from Scotland Yard’s anti-terrorist squad are still trying to piece together Litvinenko’s movements on November 1st, when it is believed he was poisoned with Polonium 210, a highly radioactive substance.

An inquest into Litvinenko’s death will open on Thursday at St Pancras Coroner’s Court. A post mortem is expected on Friday.

Even before the investigation into the death is completed, critics of Mr Putin’s rule charged yesterday that the Kremlin and its security services were responsible.

Yelena Bonner, one of the most famous dissidents from the Soviet era, said yesterday that modern Russia had returned to the practices used by the former Soviet KGB.

"I think the KGB, or the FSB as it is known, killed him," said Mrs Bonner, the widow of Andrei Sakharov the most famous Soviet dissident of his time.

"The present Russian power structure draws on the experiences it learned from Soviet operations in the past," she told The Times.

She said that she had met Litvinenko in London two years and was planning to meet his widow Marina to commiserate over the death of her husband.

Officials in Moscow have denied that the authorities had anything to do with the murder and yesterday offered to cooperate fully with British investigators.

"The prosecutor general’s office is ready to provide assistance to Scotland Yard in the inquiry into the circumstances of the death of former FSB agent Alexander Litvinenko," a spokesman for the prosecutor’s office said.

He added that no formal request had yet been made by the British authorities.
Sergei Kiriyenko, the director of Rosatom, the state nuclear agency denied that the polonium which caused Litvinenko’s death could have come from Russia.

"Allegations that someone stole it during production are absolutely unfounded," he said. "The controls are very tough."

He said that Russia exports 8 grams of polonium-210 each month to America. Exports to Russia ceased about five years ago.

Late today Boris Berezovsky issued a statement saying he was "deeply saddened" at Litvinenko's death.

"I credit him with saving my life and he remained a close friend and ally ever since. I will remember him for his bravery, his determination and his honour. All of my thoughts are with his bereaved wife Marina, his son and the rest of his family.

"Many of Mr Litvinenko’s friends and I have already publicly expressed our views about what we think might have happened. Therefore I believe the most helpful course we can take is to let the police get on with their work.

"I can confirm that traces of radiation were found in my office. This was discovered as part of an ongoing police investigation of all the locations visited by Alexander Litvinenko on 1 November 2006.

"I have complete faith in the British authorities and the police. They are conducting a thorough and professional investigation and we should now wait for the results."

Explore UK News

• Crime News

• Education News

• Health News

• Science News

• Scotland News

Times Recommends

• An officer and a gentle woman
• Dame Helen Mirren is worthy of the Epidaurus
• Foods that can help to prevent swine flu