Usain Bolt has issued a stark warning to his fellow athletes that they must stop doping otherwise track and field will die. The triple Olympic 100m and 200m champion insisted that the sport was on the mend following the staggering revelations of state-sponsored doping in Russia but conceded more needed to be done to tackle the scourge of performance-enhancing drugs.

“I don’t think it gets any worse than that,” he said, referring to the problems in Russia which he agreed had left the sport at rock bottom. “But it’s on its way back up now. Hopefully, athletes will see what’s going on and understand that if they don’t stop what they’re doing the sport will die. And hopefully they will understand what the sport is going through and what they need to do as athletes to help it move forward.”

But Bolt, who will hang up his spikes after the world championships in London which start on Friday, said he was still optimistic that these perennial problems could be tackled. “You can’t be happy about doping at all, it’s not good for the sport,” he added. “But over the years we’re doing a better job, it’s getting clean and we’re catching up to a lot of athletes. There’s an understanding that, listen, if you cheat you will get caught. Over time the sport will get better.

“I said a couple of years ago it had to get really bad, when there’s nowhere else to go but up. The only way track and field has left to go is up.”

Bolt has raced only three times this season, and last month appeared to be struggling with a back injury, but he insisted he was still the man to beat in the 100m, the qualifying rounds for which start on Friday. “For some reason I am the underdog,” he said. “That is what my team keep telling me so I have to prove myself once more. But I am confident in my abilities, always. When I go out there I am fully confident and ready to go – 100%.

“The last 100m race I ran was a 9.95sec which shows I am going in the right direction. It is all about who can keep their nerves. I have been here many times and I know I am ready. It is go time.”

Bolt, who turns 31 later this month, also gave an emphatic answer when asked how he would feel on Saturday night after the 100m final. “Unbeatable,” he said. “Usain Bolt has retired unbeatable over that event. For me that will be the biggest headline. Unbeatable and unstoppable.”

The Jamaican also insisted that he had been provided with extra motivation to win yet another world title following the tragic death of his close friend Germaine Mason, the Olympic silver medal winning high jumper, in a road accident in April.

“It was a rough time,” he said. “I have never had someone who passed away so close to me. I didn’t train for three weeks. My coach gave me my space, he gave me my time to get over it. But at some point the close net of people I was with said: ‘Listen to us, Usain, I know it is hard but you need to get back training because Germaine would have wanted it – he was looking forward to coming to your last race and seeing you compete and finishing off your legacy.’

“That really helped me get going again. It was hard. But now I really want to do it for him and his family – and all the friends that supported me in the hard times.”