He was the most active informer in the United States, responsible for 445 arrests and the seizure of more than a ton and a half of cocaine, heroin and other drugs.

Now his cover is blown and he is heading for Hollywood, and the lawyers of those he helped to jail are heading for the appeal courts.

Andrew Chambers, 43, is a native of St Louis, a former altar boy and cub scout, and a street-savvy operator who always fancied a career in law enforcement.

But his failure to achieve a college degree meant that his opportunities were limited and, after a spell in the marines, he opted for the dangerous and unconventional role of undercover informer for the drug enforcement administration (DEA).

His particular skill was making drug dealers believe he was the genuine article. His abilities earned him more than $2m in payment and expenses over a 16-year period.

He operated throughout the country, from New Orleans to Baltimore and Boston to Houston, but his greatest successes were in the Los Angeles area, where 300 of the arrests he assisted in took place.

Unlike most informers, he always claimed that he had no criminal convictions and was motivated mainly by the desire to nail drug dealers.

When giving evidence he would tell the court that he had never been arrested.

But a dogged defence lawyer from Orange county, California, Dean Steward, became suspicious.

He started investigating his background and found that he had, in fact, been arrested 16 times and had convictions for soliciting prostitutes.

Mr Steward placed a mock-up "wanted" poster of Mr Chambers on the internet to warn other defence lawyers about the informer's past.

As a result, the DEA has "deactivated" Mr Chambers and dropped charges against 15 alleged drug dealers about whom he would have testified.

With his cover blown, Mr Chambers has "come out" as an informer, to such an extent that he has been having talks about his career being the subject of a film or television series by the director Spike Lee's company.

Mary Aloe, of Proud Mary Productions in Beverly Hills, confirmed yesterday that a deal was likely and that James Manos, who has written and produced for The Sopranos, was involved.

"It's pretty hot," Ms Aloe said, adding that there were enough "funny and scary" moments in Mr Chambers's career to make a whole television series.

The successful Martin Scorcese film Goodfellas was based on the true story of an informer who was excused serious drug-dealing crimes because of the criminals he was able to help convict.

"I was truthful about what happened when the deal was going on," Mr Chambers said in an online chat after he went public earlier this month.

"I'm really an agent without a badge and a gun."

He also said he had solicited a prostitute in Denver in 1995 - she turned out to be an undercover officer - because he thought that she might lead him to a drug dealer.

He was proud of his work, assuming a variety of different identities and passing on some occasions as a Latino called "Rico".

The DEA suggest that he had lied only out of embarrassment and that other dishonest areas of his life which came under scrutiny, such as inaccurate tax returns, should not affect the reliability of his evidence.

They point to the fact that 95% of the defendants in the cases in which he was an informer pleaded guilty.

Defence lawyers disagree, and are now re-examining 295 cases in which he was involved.

"When you get a guy who would lie about just about everything else, why do you think he would tell the truth about what led up to the deal?" Mr Steward said after the news of Mr Chambers's background broke.

"It's a corrupting system," a leading Californian defence lawyer, Ian Loveseth, said yesterday.

"There's money flowing every which way. These guys make money, they do stings, they're professional.

"It's corrupting to the agency because they're forced to condone perjury. You start violating the oath on something morally defensible and - hey - you pay the price."

The exposure of Mr Chambers and his subsequent appearances on television will have an inevitable effect on the DEA's work.

He was the most active of their 4,000 informers and, until now, defence lawyers could not suggest that he was motivated by a desire to save his own skin.