The wife of murdered Russian ex-spy Alexander Litvinenko launched The Litvinenko Justice Foundation this week to help put pressure on the British and Russian governments to find those responsible for his death.

Marina Litvinenko was joined at the event in Whitehall by her husband's friends Alex Goldfarb and Russian billionaire Boris Berezovsky, who gave £250,000 to the new charity.

The foundation aims to ensure the Russian and UK governments find Mr Litvinenko's killers, to prevent a similar incident happening again and to seek compensation for those who were exposed to Polonium-210.

Mr Litvinenko, who lived in Osier Crescent, Muswell Hill, with his wife and their 12-year-old son, Anatoly, died last November from radiation poisoning after ingesting Polonium-210. The 43-year-old made a statement from his deathbed accusing Russian president Vladimir Putin of being behind his murder, which the Kremlin has strenuously denied.

Mrs Litvinenko said: "I said in a letter to President Putin that I will not rest until Sasha's killers are brought to justice. The Litvinenko Justice Foundation will campaign vigorously for that. I also never want to see anyone else lose their husband to such a murder."

Mr Berezovsky said that his cash would not be used directly to pay compensation to those contaminated with Polonium-210, the money would be used for a legal campaign to win compensation. A letter from the foundation has been sent to Prime Minister Tony Blair, Home Secretary John Reid and Attorney General Lord Goldsmith, asking for reassurance that any suspects would stand trial in this country.

The Metropolitan Police has submitted a file of evidence on the case to the Crown Prosecution Service.