MEDICAL experts have identified the type of dioxin used to poison Ukraine’s opposition leader, Viktor Yushchenko, in a major breakthrough in his efforts to identify the culprit.

Mr Yushchenko has forbidden them from disclosing the results, to avoid influencing the re-run of his presidential run-off with the Prime Minister, Viktor Yanukovych, on December 26. Mr Yushchenko, a Western-leaning former central banker, said yesterday that his opponent was planning unspecified “provocations” that could jeopardise the vote.

He also said for the first time that he was sure he had been poisoned at a dinner with the head of the Ukrainian Security Service, Igor Smeshko, and his deputy, Volodymyr Satsyuk, on September 5, the night he fell ill.

Yesterday’s test results are expected to provide compelling evidence for his claim and further incriminate Mr Yanukovych’s Government and his powerful backers in Ukraine and in Russia. Mr Yushchenko’s supporters have suggested that Russia ordered the poisoning to prevent the opposition leader, who advocates joining the European Union and Nato, from winning the election.

Last week doctors confirmed that Mr Yushchenko had been poisoned with dioxin, probably given to him in a creamy soup, but they could not say what type of dioxin or prove that it had been an assassination attempt. Further tests at three laboratories identified yesterday the precise type of dioxin — the crucial fingerprint that could prove it was administered deliberately and reveal its origin, as well as its long-term effects on his health.

The head of one of the laboratories, BioDetection Systems in Amsterdam, told The Times that all three laboratories had identified the same dioxin, but he refused to name it. “The results match very well. They are definite,” he said. “We just need to know what the family wants us to do.”

He said that Mr Yushchenko’s wife had called Michael Zimpfer, the head of the Rudolfinerhaus clinic in Vienna where her husband was treated, to ask that the results be kept secret until after the election. Dr Zimpfer and other doctors at the clinic were not available for comment.

However, senior toxicologists said that they believed the dioxin was the compound 2,3,7,8-tetrachlorodibenzo-p-dioxin or “TCDD” — a component of Agent Orange, the defoliant used by the United States in the Vietnam War. “It’s the best known and it’s pretty toxic,” John Henry said. “In the old Soviet Union they would have studied these chemicals in detail. They may well know more about the acute effects of dioxin poisoning than we do.”

Since acute dioxin poisoning was almost unheard of in the West, nobody would have recognised the symptoms and tested for dioxin had Mr Yushchenko died, he said.

Dr Henry, one of Britain’s top toxicologists, was one of the first people to suggest that Mr Yushchenko had dioxin poisoning, after seeing a photograph of the lesions and cysts he had developed on his face.

Tests this week showed Mr Yushchenko had 6,000 times the normal level of dioxin in his system — the second highest level ever recorded in a human being.

Yesterday’s results could reveal where the dioxin came from by identifying the isomers of the chemicals used, Dr Henry said. “You could pinpoint it to a certain country, even a laboratory,” he said. The results will be handed to Ukrainian prosecutors and MPs who have reopened an investigation.

Mr Yushchenko has pledged that the culprits will be prosecuted but said that an investigation should wait until after the election. “There is not a 100 per cent guarantee that the election will take place,” he told a news conference in Kiev yesterday. “I know of provocations being prepared in the eastern regions.” Mr Yanukovych said this week that thousands of his supporters were volunteering to help to prevent Mr Yushchenko from winning.

The Prime Minister says the protests that paralysed the nation after the fraud-ridden November 21 vote amounted to a US-financed coup d’état.

Today Mr Yushchenko is to travel to Russian-speaking eastern Ukraine in an attempt to expand his support base beyond the Ukrainian-speaking West.

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