Italian Mario Scaramella told a Rome press conference that he met Alexander Litvinenko the day he fell ill.

Toxicologist Professor John Henry earlier said that ex-KGB agent Mr Litvinenko may have been poisoned with a radioactive substance.

Scotland Yard anti-terrorist officers have taken charge of the investigation.

Officers have said they are treating the case as a suspected "deliberate poisoning".

Other symptoms

BBC Rome correspondent Christian Fraser said Mr Scaramella, who is involved in an Italian parliamentary inquiry into KGB activity, was sufficiently worried by the contents of an e-mail to ask for advice from Mr Litvinenko.

He said he met the Russian in a London sushi bar on 1 November for 35 minutes to discuss the e-mail.

He said Mr Litvinenko had promised to look into the message but when Mr Scaramella called him later that night the Russian was already falling ill.

"It's not 100% thallium," Dr Henry said outside University College Hospital.

He said if it was radioactive thallium it would now be difficult to trace.

"The levels of thallium present in this case are lower than expected. Mr Litvinenko also has signs and symptoms that are unexpected and do not normally occur with thallium poisoning, especially the fact that his bone marrow is not functioning and his white cell count has dropped to zero.

"Something other than thallium is involved... at this stage radioactive thallium seems the most likely cause," he said.

Radioactive thallium is used in hospitals, but Dr Henry said it was not used in massive doses consistent with Mr Litvinenko's condition.

'Sheer nonsense'

"Poisons can be taken by mouth, they can be injected, they can be inhaled," he said.

"In this case his symptoms are gastro-intestinal so the probability is that he has swallowed something that is poisoned.

Prof David Coggon, Professor Of Occupational And Environmental Medicine, said: "The nature and risk of adverse effects from radioactivity will depend on where the thallium gets to in the body, in what quantities, how long it stays there, and what type of radiation is produced."

The hospital said Mr Litvinenko's condition was unchanged overnight.

Friends of Mr Litvinenko have alleged he was poisoned because he was critical of the Russian government.

Kremlin spokesman Dmitry Peskov said they did not want to comment about the accusations, which they called "sheer nonsense".

Russia's foreign intelligence service also denied involvement.

Mr Litvinenko fled to the UK in 2000 and was granted asylum

In a statement on Tuesday, University College Hospital said: "Mr Litvinenko's condition remains unchanged from yesterday. He remains in a serious condition in intensive care."

Mr Litvinenko had been investigating the murder of Russian journalist Anna Politkovskaya, an outspoken critic of Mr Putin and Russian policy in Chechnya, who was shot dead at her Moscow apartment building last month.

Doctors had told Mr Litvinenko he had a 50/50 chance of surviving the next three to four weeks, said Alex Goldfarb, who has been visiting him.

Source: BBC News