The poisoning of Ukrainian President Viktor Yushchenko in 2004 has led to a breakthrough in the treatment of dioxin cases, a skin specialist said on Wednesday, according to Reuters.

Professor Jean-Hilaire Saurat told a news conference the amount of the chemical found in Yushchenko`s body could not have been ingested by accident and could not have been faked.

The president, whose face and body were disfigured by the poisoning, took in 1,000 times more dioxin than is normally present in the human body.

It was believed the pockmarks and lesions were caused by the dioxin but the Yushchenko case had shown that they were effectively "small livers" created by the body under the skin to absorb the poison and destroy it, Saurat said.

Head of dermatology at Geneva`s University Hospital, he led a team of international and Ukrainian doctors who have made a detailed study of the Yushchenko incident.

It occurred when the then-opposition leader was campaigning for the presidency on a pro-Western ticket.

Yushchenko, now 53, subsequently won the presidency in a re-run poll after Ukraine`s Supreme Court, amid street protests dubbed the "Orange Revolution," struck down the results of a first vote that gave victory to a pro-Moscow candidate.

"There is no doubt whatsoever that this was a very serious case of dioxin poisoning ... there is no other way that that amount could have got into his body by accident," said Saurat.

Yushchenko said he knows who was responsible and they were all in Russia. Yushchenko has also accused Moscow of hindering the investigation.

Saurat, and the president`s personal physician Rostislav Valikhnovsky, said they were speaking out because of allegations circulating in Kiev that Yushchenko had staged the poisoning to win support in 2004.

Yushchenko said in October he had undergone 24 full operations in Ukraine and abroad as doctors struggled to bring him back to full health, a battle Saurat said now looked to have been largely successful.

The Geneva professor said the Ukrainian leader had also undergone dozens of smaller operations. "In the first three years after the poisoning, he suffered constant severe pain -- like torture -- which is what happens with dioxin," he said.

The professor said the case had revealed details about dioxin and its effects which "will be invaluable in managing any case of massive dioxin poisoning in the 21st century".

The pockmarks were in fact part of the body`s defensive reaction, he said. Because of this the condition had been named ADISH, or Acquired Dioxin-Induced Skin Haematoma.

Similar reactions had been observed in dioxin victims in the past, including those who suffered from a chemical factory leak in Seveso, Italy, in 1976.