Russian distance runner Olga Yegorova will be allowed to compete at the World Athletics Championships despite failing a drug test.

The world indoor 3000m champion had been suspended by the International Amateur Athletics Federation (IAAF) when she tested positive for the endurance-boosting drug EPO.

The IAAF has dismissed the case because of a legal blunder. Yegorova was suspended after she tested positive at the Golden League meeting in Paris last month.

"For rule and legal reasons the IAAF has no choice but to lift the ban on the athlete," said Arne Ljunqvist, head of the IAAF anti-doping commission.

Boycott threatened

The French authorities who had carried out the EPO test had failed to follow the rules which insist that both urine and blood must be analysed, Ljunqvist added.

Plans to re-test the 'B' sample after a technical error was abandoned by the IAAF.

"The reason why the 'A' test is invalid is because the French authorities did not do a blood test as well," said the Swede.

Defending world and Olympic 5000m champion Gabriela Szabo of Romania has threatened to boycott the race if Yegorova is allowed to compete.