The source told BeverageDaily.com it was "embarrassing" the Food and Drug Administration had failed to eradicate benzene residues from all drinks.
His comments come as newly released meeting memos show at least one soft drinks maker, Kraft Foods, called for more guidance on benzene in soft drinks from the US Food and Drug Administration (FDA) earlier this year.
The developments put pressure on the FDA nine months after a BeverageDaily.com investigation revealed the watchdog had again found some drinks containing more benzene than is allowed in US drinking water. Benzene causes cancer if consumed in enough quantities over a sustained period.
Both FDA and industry had known of the source, a reaction in drinks between two common ingredients - sodium benzoate and ascorbic or citric acid - for 15 years.
"Big companies are very powerful. If you're a regulator with a tight budget, it could have been one of those closets with skeletons in that you don't want to open," the ex-FDA enforcement official told BeverageDaily.com.
The FDA agreed in 1991 for firms to "get the word out and reformulate" privately, without an official guide or limit drawn up. But isolated drinks samples continued to show elevated benzene levels in later FDA Total Diet Surveys.
There is little health risk linked to the levels of benzene found in drinks, according to both the FDA and soft drinks industry.
"There is a difference here between a small and unavoidable risk, and a small but avoidable risk," the ex-agency source said.
"The FDA seems to think the risk is quite low here. On the other hand, it's in a [non-essential] product nobody needs, and it doesn't have to be there. They claim they can reformulate."
He said he was "not proud" the FDA had kept the issue quiet from the public. "Even if they didn't have a case they could bring, nobody told the consumer. This administration is much more tuned to industry rather than consumer needs."
Some in the soft drinks industry appear to have wanted a better lead from the FDA too.
Kraft Foods recently reformulated all of its ready-to-drink beverages containing sodium benzoate and ascorbic acid to limit benzene formation, according to an internal FDA meeting memo from this year.
The same memo noted Kraft's warning that "there is no one solution that can be applied to all beverages [to mitigate benzene formation]". To cope with this, Kraft said "general guidance on this issue from FDA could help to institutionalise the need to pay attention to several variables to prevent future occurrences".
Kraft was one of several high profile soft drinks firms, also including Coca-Cola and PepsiCo, which were hit by lawsuits over benzene this spring.
An industry-wide guidance document on limiting benzene in drinks, the first to be compiled, was published by the International Council of Beverages Associations after the issue went public this year.
Several points, including the potential protective power of additive EDTA, the power of heat to increase the reaction and the higher risk associated with diet and sugar-free drinks, were stated in an internal FDA memo dated January 1991.