Rob Hayles, the Olympic medallist and ex-world champion, has been "withdrawn from competitions" for two weeks following an anomaly in a blood test.

The ban means he will miss the Track Cycling World Championships after the test showed levels of haematocrit, the percentage of red blood cells in a person's blood, exceeding international governing body rules. Dutch rider Pim Ligthart has also been suspended for 14 days after a blood test.

Cycling's international governing body, the UCI, announced that during a routine health check the Britain Cycling Team member had recorded an anomaly in his results.

That anomaly was confirmed as the level of haematocrit was 50.3 per cent, slightly higher than the permitted 50 per cent.

While the results require further investigation, Hayles is not under suspicion as the test does not provide proof of blood doping.

Hayles, who won two silver medals at the 2004 Olympics, was due to compete in the individual pursuit event at this week's World Track Championships in Manchester, but will now undergo further checks as British Cycling work with the UCI to determine the reason for the anomaly.

Dave Brailsford, British Cycling performance director, said: "I am sure there is an honest explanation. I am astonished and disappointed for Rob and frustrated for the team.

"But at the end of the day I think the truth will prevail as always. I welcome the screening system I think it is a great thing. I think we should be subject to it and I would like to see other nations subject to it."

"This is not the first time this has happened to several riders and you tend to find that there are subsequent tests that are then actually verified by the UCI. They come back and said everything is fine.

"I have known Rob a long time and there has never been any doubt in my mind that he has been anything but a fantastic athlete for Britain. He does not take drugs."

High haematocrit levels can be an indicator of use of the blood booster EPO. Riders who fail the tests are automatically given a two-week suspension on health grounds.

The UCI said it had carried out 66 tests early Wednesday on the American, Australian, Dutch and British teams.

Dr. Tjeerd Devries, the Netherlands' team doctor, said that for the past week, Ligthart had been suffering from gastroenteritis and was taking medication, including paracetamol.

Devries said there had been a "discrepancy," which was not "too high" in just one of at least four tests. "We will carry out extensive tests on the rider," he added.

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