International Association of Athletics Fedeations (IAAF) President Sebastian Coe needs to start introducing new policies to deal with doping and corruption as soon as possible to start restoring everyone's trust in the sport, four-time Olympic gold medallist Michael Johnson warned today.

Athletics is currently reeling from a series of scandals, including allegations of state-supported doping in Russia, leading to the country being suspended by the IAAF.

Coe's predecessor Lamine Diack is also currently under investigation in France for accepting money from Russian athletes to help cover up positive drugs tests.

“Seb Coe certainly has his work cut out for him, not just with doping issues but with credibility and restoring credibility to the sport," Johnson, currently in Dubai where he is attending the HSBC World Sevens Series in his new role of mentoring the United States rugby team, said today.

"It is a critical moment for the sport and Seb will have to lead by example, also in implementing policies that will restore credibility back in the sport.

“Credibility has to be restored, whether it can or not we will have to see.

"But that is important: it has to be priority, not only with media, but also with fans and athletes, credibility has to be restored – that has to be the first priority,”

Johnson, winner of the Olympic 200 and 400 metres at Atlanta 1996, is earmarked for a leading role in the new Values Commission Coe is planning to launch to help support and guide athletes, particularly teenagers, when confronted with dangers such as illegal betting and nationality or age manipulation, as well as doping.

“Athletics, I believe, has done a very good job of having a zero-tolerance policy for doping," the American sprinter, who holds the world record for 400m, said.

"The issue is, though, when you move from the conversation being less about who may or may not be doping to whether the organisation entrusted with keeping the sport clean and policing the sport, whether or not they are complicit in covering up tests and protecting athletes and there’s corruption and bribery allegations, that’s a whole different ballgame.”

Coe also received support from another former athlete, his ex-rival Steve Cram, Britain's former world record holder for the 1500m and mile.

“What would happen if Seb is not the IAAF President?" Cram said at a conference he was speaking at in Singapore today.

"Who else could do it?

"Seb has got to be allowed the time to get athletics right.

"It is a huge opportunity to make a real impact, to do what he has done in the past, too - to be a real leader.”

Johnson, though, admitted that stamping out doping in athletics totally is not achievable.

“I don’t think anyone in the world thinks we’re going to get down to zero-doping," he said.

"Doping is cheating, right?

“Are we ever going to get to a point where no one cheats on anything? I think that’s unrealistic."