"The association between [passive smoke] and coronary heart disease and lung cancer may be considerably weaker than generally believed" claimed the study, in the weekly British Medical Journal.

In a surprising twist, the study was backed by anti-smoking crusader Dr. Elizabeth Whelan.

"There is simply no convincing evidence linking secondhand smoke to lung cancer and heart disease," said Whelan, an epidemiologist and president of the American Council on Science and Health.

Whelan, author of "A Smoking Gun: How the Cigarette Industry Gets Away with Murder," said her group's research has reached the same conclusion as the new study.

While Whelan said she's delighted by New York City's smoking ban, she labels "patently absurd" Mayor Bloomberg's claim that it would prevent 1,000 deaths of bar and restaurant workers.

Exposure to cigarettes has "definite, acute health effects" - such as ear infections, respiratory problems and asthma, Whelan said.

But she estimated the deaths prevented by the city's rule would be "between zero and a hypothetical 10 to 15" - and the deaths would likely be from asthma attacks.

"The best way to lose an argument is to overstate it, as I fear Mr. Bloomberg has done," Whelan said.

The British Medical Association called the report "fundamentally flawed," and said it was based on questionable data.