MURDERED ex-Russian spy Alexander Litvinenko was involved in a blackmail scheme before his death, a US television documentary has claimed.

A 60 Minutes report aired on CBS last night claimed that in the months before his death Mr Litvinenko needed money and a job.

His backer in London, billionaire Russian exile Boris Berezovsky, told the program that he had reduced his financial support for the ex-spy.

A Russian graduate student, Julia Svetlichnaya, who sought out Mr Litvinenko's help on a book she was writing, said he told her about his new "project".

"He told me that, at that moment, he's doing a project for blackmailing one of the Russian oligarchs which resides in UK," Ms Svetlichnaya told 60 Minutes.

"He thought that it was actually an ok thing to do because this particular person, as Mr Litvinenko claimed, had a connection with the Kremlin, had a connection with (Russian President) Putin. And so in his view it, was ok to blackmail him.

Mr Litvinenko was poisoned with the radioactive isotope polonium-210 in London last year.

In a statement dictated on his deathbed he blamed Putin for his murder.

Ms Svetlichnaya added: "That's what he did, gather information on people. So it didn't sound out of place completely to me, the blackmail story.

"He mentioned blackmail in a very casual, casual manner. Every time I met him, he somehow told me he needs money. He needs to make a living. He's got children to feed."

According to the report, the pair met several times last spring. At a meeting in Hyde Park, they walked around for hours because Mr Litvinenko said that professionals keep moving so "no one can eavesdrop on their conversations".

His wife, Maria, said she didn't know what her husband was doing, but said he was not a blackmailer. "Never, never. Sasha wasn't a person in this way," she told the program.

Polonium-210 is found in the environment and at low concentrations in people and poses a risk only if inhaled, swallowed or ingested through an open wound.

In the two months since Mr Litvinenko died at University College Hospital, 14 people have tested positive to low levels of the radioactive isotope.

Last week, the Health Protection Agency said it had found low levels of radiation contamination at the Pescatori restaurant in Mayfair, central London.

The HPA said it did not anticipate "any significant health risk" to staff or customers of the restaurant.