Carl Lewis has broken his silence on allegations that he was the beneficiary of a drugs cover-up, admitting he had tested positive for banned substances but claiming he was just one of "hundreds" of American athletes who were allowed to escape bans.

"There were hundreds of people getting off," he said. "Everyone was treated the same."

Lewis has now acknowledged that he failed three tests during the 1988 US Olympic trials, which under international rules at the time should have prevented him from competing in the Seoul games two months later.

The admission is a further embarrassment for the United States Olympic Committee, which had initially denied claims that 114 positive tests between 1988 and 2000 were covered up. It will add weight to calls by leading anti-doping officials and top athletes for an independent inquiry into the US's record on drug issues.

Last week Dr Wade Exum alleged that a ban imposed on Lewis after positive tests for three stimulants had been overturned by the USOC when the athlete said he had ingested them mistakenly in a herbal supplement.

Lewis received only a warning after officials ruled that his positive tests were due to "inadvertent" use. Some scientists believe the substances could have been a masking agent for more serious drugs, such as anabolic steroids.

"The climate was different then," said Lewis. "Over the years a lot of people will sit around and debate that [the drug] does something. There really is no pure evidence to show that it does something. It does nothing."

Lewis, who was arrested in Los Angeles on Monday for suspected drink-driving which friends say was the result of depression over Exum's revelations, won the 100 metres gold medal in the 1988 Seoul Olympics after Canada's Ben Johnson was stripped of the title when he tested positive for a steroid.

Lewis also won the long jump and finished second in the 200m behind his training partner Joe DeLoach, also named by Exum as having escaped a ban.

Johnson has now demanded that Lewis be stripped of his medals from Seoul, although the International Olympic Committee has no plans to review the situation because it has a statute of limitation set at three years.

"Do you expect him to say anything different?" said Lewis. "I mean we're talking about Ben Johnson. Come on. Let's be realistic."

Lewis, 41, said he was not concerned about the uproar around the world caused by the revelations. "It's ridiculous. Who cares?" he said. "I did 18 years of track and field and I've been retired five years, and they're still talking about me, so I guess I still have it."

Moscow is to launch its bid for the 2012 Olympic Games by staging the richest meeting in athletics history, offering a $1m (£630,000) purse to anyone who breaks the 100m world record.

Britain's Dwain Chambers will join the United States' world record holder Tim Montgomery and the Olympic and world champion Maurice Greene in an event in which the winner is guaranteed $500,000, nearly 10 times what the gold medallist in the world championships in Paris will earn. Nine other events, including the triple jump in which Jonathan Edwards is expected to compete, will split a prize purse of $3.5m.

Organisers are predicting a sell-out crowd of 85,000 at the meeting on September 20 in the Luzhniki Stadium, the arena for the 1980 Olympics and the centrepiece of Moscow's bid for the 2012 games, for which its rivals are expected to include London.

The event is being staged with the assistance of Stellar, the British-based management company headed by the former European 200m champion John Regis. "Moscow wants to show it can put on the best meeting in the world to help promote their Olympic bid," said Stellar's Mark Brodie. "It's going to be spectacular."