The move is part of a general anti-doping drive but also aims to avoid the potential for any embarrassment at the Games themselves.

British Olympic chiefs have told drug testers UK Sport to enact the plan.

UK Sport's John Scott said: "It is our intention to test every athlete before they go to Athens and we are confident that will be achievable."

Meanwhile, laboratories are continuing to work through about 1,000 samples taken previously with the new test to uncover the designer steroid THG.

Dwain Chambers received a two-year ban for taking the substance earlier this week.

So far, two thirds of the samples have been tested but no new positive findings have come to light.

UK Sport is also anticipating a rise in its workload over the next year and has agreed to begin sending samples to a laboratory in Newmarket.

Until now, the lab has specialised in testing horses for doping and should be accredited by the World Anti-Doping Agency in May.