Police chiefs say that officers were not adequately informed of the risks of polonium-210, the substance used to kill the former KGB spy. Two detectives working on the case have been contaminated with radioactive poisoning and are said to be “terrified and upset” that they may develop cancer.

Authorities suspect that Litvinenko was poisoned on November 1 at the Pine Bar, in the Millennium Hotel in London, but they told the 250 people who were there that day that they were in no danger. Now they are trying find them to run health checks.

There is concern that Islamic terrorists could release a dirty bomb, which mixes explosives with low-level radioactive substances. John Reid, the Home Secretary, said yesterday that the terrorist threat facing Britain at present was “very high indeed”. He told the Sunday Programme on ITV1 that the chances of an attempted attack over Christmas were “highly likely”, and that 30 conspiracies had been uncovered.

Whitehall chiefs think the contingency plans should be revised in the light of the Litvinenko case. A senior police source told The Times: “We thought we had a game plan. Clearly this episode has shown there are shortcomings. We need to think again how the emergency services should treat a radiological scare, the training the emergency services require and how to alert the public without causing panic.”

Experts are apparently still giving contradictory advice. On the Health Protection Agency’s website the agency says that polonium-210 is “not a radiological hazard as long as it remains outside the body” and that “most traces can be eliminated through hand-washing, washing machines and dishwasher cycles for clothes, plates, etc”.

However, the only contact one of the contaminated detectives had with the poison was when he removed items such as clothing from Litvinenko’s home. Evidence of the substance was reportedly found in a tea cup at the Millennium Hotel more than a month after Litvinenko was killed and countless washes. Seven bar staff who had minimal contact with Litvinenko all show evidence of exposure.

The agency said last week that Mario Scaramella, the Italian security expert who met Litvinenko on the day he fell ill, had “significant amounts” of polonium-210 in his system. Mr Scaramella has been told he is all clear and that the dose is “significantly less than from one year’s natural background radiation”. The police source said: “Frankly the public don’t know what to believe at the moment about the risks polonium-210 causes.”

Police chiefs recognise that contamination tests would cause a panic if they were held in the aftermath of a radiological attack. The source said: “There is a problem of public concern if you have Geiger counters going off.”

Last month Dhiren Barot, 34, of London, was jailed for 40 years for plotting terrorist attacks, including the use of dirty bombs.

Nick Priest, a radiology expert at Middlesex University, said yesterday that terrorists were unlikely to use polonium-210 as it was hard to find in Britain and difficult to import. But, he said, there were other radioactive materials they could use.

Plans have been drawn up for officers to seal off contaminated areas and protective suit training has been given 7,000 officers across Britain. In London, mobile units, which would become the spearhead of the police operation, now carry small radioactivity alerts.

In the Litvinenko murder investigation police have reached a stalemate with Russian officials, who insist that their own inquiry must take priority. Yuri Chaika, the Prosecutor-General, wants to send a team of his investigators to London, arguing that the case involved the murder of a Russian citizen and the attempted murder of two others.

The stand-off surrounds Mr Chaika’s demand that Russian detectives interview a number of known dissidents, such as the exiled oligarch Boris Berezovsky, who he claims has information about the poison plot. Diplomats from Britain point out that British authorities cannot force the likes of Mr Berezovsky to co-operate with the Russian inquiry.

British detectives have been told until now that they cannot interview Andrei Lugovoy, a former KGB agent who met Litvinenko on the day he fell ill, because he is unwell, despite claims to the contrary by Mr Lugovoy’s lawyer.

• A television advertisement revealing that cigarettes contain polonium-210 has been withdrawn by the Government because of the current “sensitivities”. The Department of Health said that the campaign — which was commissioned before Litvinenko’s death — would be shown in the future.

Times Recommends

• Riots as Zimbabwe turns off water supply
• Tourists told to stay away amid Venice floods
• Protest is no picnic for Carrefour customers