One of Britain's best hopes for a gold medal at next year's Olympic Games, Chambers allegedly failed a test for the newly discovered drug tetrahydrogestrinone (THG) which, until last week, was thought to be undetectable.

Traces of the drug were found in a urine sample that the European 100 metres champion and record holder provided during an out-of-competition test at his training base in Saarbrucken, Germany, on August 1, the Guardian newspaper reported.

Chambers is reported to have returned a positive 'A' sample. A second, or 'B' sample, is yet to be tested.

If Chambers were to fail that test he would be banned from athletics for two years and from the Olympic Games for life.

Chambers's management company was referring all queries to the athlete's lawyer who was not available for comment when contacted by Reuters.

However, the athlete's U.S.-based Ukrainian coach, 71-year-old Remi Korchemney, spoke out for the Briton.

Korchemney said he had not yet talked to Chambers but he angrily denied that Chambers would test positive for a steroid.

"This is not something the public should just accept," Korchemney told the San Jose Mercury News.

NEW STEROID

"Can you say someone is guilty without a judge and jury? You are supposed to be innocent until proven guilty."

The reports that Chambers had tested positive came a day after the IAAF said all urine samples from the Paris world athletics championships in August would be re-tested.

Athletics' governing body took the decision following an announcement by the U.S. Anti-Doping Agency (USADA) last Thursday that several American athletes had tested positive for a new steroid tetrahydrogestrinone (THG).

The positive samples were found in the re-testing of 350 doping samples from the U.S. athletics championships in June.

"I know of no other drug bust that is larger than this involving the number of athletes we have involved, certainly in the anabolic steroid area," said USADA chief executive officer Terry Madden.

"This is a conspiracy involving chemists, coaches and certain athletes using what they developed to be 'undetectable' designer steroids to defraud their fellow competitors and the American and world public who pay to attend sports events."

A test for the drug was discovered by the IOC-accredited laboratory in Los Angeles after an unidentified man sent them a syringe containing THG.

Madden said the man, who said he was a high-profile coach, called the USADA in June alleging that leading track and field athletes were using the steroid because no test existed.