UK Anti-Doping informed the athlete on February 28 and imposed a provisional suspension, pending a hearing.

"This gives a very clear message to athletes that you will be regularly tested to ensure a clean and fair sport," said British Bobsleigh performance director Gary Anderson.

A guilty verdict ordinarily carries a two-year ban from competition.

The athlete will not be named until their case has been assessed by UK Anti-Doping and a verdict delivered.

"The athlete now has the opportunity to respond to the charge, including the right to a full hearing and testing of their B sample," Anderson said in a statement to the GB squad.

"British Bobsleigh will not be making any further comment on the issue until after the full process of investigation has been completed."

Although mitigating circumstances could reduce any potential penalty, a two-year ban would see the athlete miss the 2014 Winter Olympics in Sochi.

Bobsleigh is Great Britain's most successful winter sport – they have won one gold, one silver and two bronze medals at senior Olympic Games – but  the British bobsleigh team had a difficult Vancouver 2010 Winter Olympics, where they failed to win a medal, and last year saw brakewoman Serita Shone fracture her spine.

However, they had produced some positive headlines in recent months, with Mica McNeil and Jazmin Sawyers winning silver at this year's inaugural Innsbruck Youth Winter Olympics.

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