LONDON • Sebastian Coe, the president of athletics' embattled world governing body, has insisted that there is no agreed time frame for Russia's return to world competition following systemic doping revelations.

In a new report by ARD's Hajo Seppelt, he also admitted that he has not seen the August documentary that contained allegations that the International Association of Athletics Federations failed to follow up on hundreds of suspicious blood tests and prompted him to declare they amounted to a "war on my sport".

Coe, who will this week face a British parliamentary select committee, said he had been travelling at the time and read a transcript of the programme instead.

In the new film, by the German journalist whose incendiary documentary 12 months ago exposed the extent of state-sponsored doping in Russia, Coe conceded the effects of performance-enhancing drugs could remain in athletes' systems beyond their ban.

"This is a historic challenge as well. Longitudinal studies have shown almost conclusively that athletes that have used performance-enhancing drugs - particularly some of those muscle growth drugs - have that benefit for many years to come," said Coe.

He also said he had never had the opportunity to meet the whistleblowers, Vitaliy Stepanov and his wife Yuliya, who made the undercover videos that formed a key plank of evidence in Seppelt's report and Dick Pound's later damning independent report for the World Anti-Doping Agency (Wada).

The Stepanovs, now living abroad, were specifically singled out for praise by Pound, who called for a culture change in the treatment of whistleblowers by sport in general.

Russian officials have said they will do all they can to return to competition in time for next year's Rio Olympics and the International Olympic Committee president, Thomas Bach, has said that he expects them to do so.

THE GUARDIAN