Usain Bolt launched a passionate defence of his record-breaking achievements as he spoke yesterday about the drug scandal involving two of his leading rivals.

The Jamaican said athletics has been hurt by the positive tests for his compatriot Asafa Powell and American Tyson Gay. But the world record holder and double Olympic champion over 100 and 200m insisted fans should have confidence he is no drugs cheat as he prepared for this weekend's Anniversary Games.

He said: "If you were following me since 2002 you would know I have been doing phenomenal things since I was 15. I was the youngest person to win the world junior title at 15, I ran the world junior record at 18. I have broken every record there is to break, in every event I have ever done. For me, I have proven myself since I was 15. I have shown I was always going to be great."

He added: "I was made to inspire people and to run. I was given a gift and that's what I do. I am confident in myself and my team, the people I work with. And I know I am clean."

The recent revelations are the most serious doping scandal to surface in athletics since the BALCO episode involving Marion Jones, and Britain's Dwain Chambers, who will compete against Bolt tonight in the 100m.

The race will also feature James Dasaolu – who ran 9.91 seconds at the British Championships in Birmingham to become the second fastest Briton in history over the distance. "I'm really happy just to be among the likes of Usain Bolt and the quickest guys in the world," Dasaolu said. "I know I have to run quicker if I am to challenge him and the rest, but I am progressing pretty well. I have broken that sub-10 barrier so lining up against sub-10 guys I know that's the kind of the field I belong in. It gives me confidence. This is what I work hard for every day."

Dasaolu's time is faster than Bolt has run this year, with Bolt's best in 2013 9.94sec. The Jamaican is running the 4x100m relay tomorrow in a meeting that will be his first competition in the UK, the London Olympics aside, since 2009.

Gay and Powell, the second and fourth fastest men in history, are still waiting for the results of their 'B' samples, and Bolt said it is important not to speculate too much at this stage. "I think there are a lot of details left to be discussed," he said.

Powell's failed test for the banned stimulant oxilofrine has been blamed by his camp on new nutritional supplements. Bolt said he does not use supplements, and added: "I take vitamins, every athlete takes vitamins."

The 26-year-old has been in contact with Powell by text since the news of his failed test and told him to "stay strong and stay focused". "I didn't want to bombard him with questions," he added. "I told him, 'Sorry to hear what was going on.' And he said, 'Yes, it's kind of rough, it's hard."'

Bolt said he was tested on Tuesday and expects to be randomly tested "all the time". "In life things happen, people make mistakes, mishaps happen. I can't determine what the rules should be - [but] drugs are harsh on the sport."