NEW YORK - A leading American AIDS group said it was suing Pfizer, the producer of Viagra, accusing the company of increasing the spread of sexually-transmitted diseases through "irresponsible" marketing.

AIDS Healthcare Foundation, the largest AIDS healthcare, prevention and education provider in the United States, accused Pfizer of deliberately pitching the erectile-dysfunction drug at men who did not need it.

This undated file photo shows Viagra pills made by Pfizer. A leading American AIDS group said it was suing Pfizer, the producer of Viagra, accusing the company of increasing the spread of sexually-transmitted diseases through "irresponsible" marketing. [AFP]

"Pfizer's direct to consumer marketing of Viagra as a drug to enhance sexual performance is primarily aimed at men who don't necessarily suffer from a clinical diagnosis of erectile dysfunction," the group's president, Michael Weinstein, said in a statement.

"We believe it is not only irresponsible, but also illegal, especially in light of the drug's known use as part of a 'circuit party cocktail' of drugs that is fueling the spread of STDs and HIV," he added.

Viagra has become increasingly popular on the club circuit to counteract the side effect of erectile dysfunction associated with the use of party drugs such as ecstasy, amphetamine and crystal methamphetamine.

The case is being brought under a Californian law and accuses Pfizer of "unlawful, unfair and fraudulent business practices."

The lawsuit alleges that Pfizer's "unlawful and deceptive marketing of its erectile dysfunction drug Viagra has caused an increase in the spread of sexually transmitted diseases including, but not limited to, HIV/AIDS."

It further accuses Pfizer of maintaining its marketing strategy despite what the group says is "clear evidence of its illegality and harmful effects."

Weinstein said the lawsuit was aimed to force Pfizer to stop advertising the medication "in the reckless manner it has been doing" and require the company to undertake a public information campaign about the alleged risks of Viagra.

The lawsuit specifically outlines what the AIDS Healthcare Foundation calls "the increased risks of transmission of sexually transmitted diseases associated with using Pfizer's Viagra."

Pfizer dismissed the allegations, saying in a statement that its advertising made clear Viagra does not protect against sexually transmitted diseases, while rejecting claims it was promoting the recreational use of the drug.

"Pfizer does not promote Viagra for recreational use. We have always been committed to safe and appropriate use of Viagra for the treatment of erectile dysfunction," the statement said.

"Pfizer recognizes that the transmission of HIV and other sexually transmitted diseases is a significant public health issue," it added.

In late 2005, the AIDS Healthcare Foundation demanded Pfizer withdraw an advertising campaign that suggested using Viagra to ring in the new year.

"What are you doing New Year's Eve?," said the advertisement, which appeared in national newspapers, showing a middle-aged man with greying hair.

"It is an outrage that, by referencing the biggest party night of the year, Pfizer would employ an advertising strategy that encourages the use of Viagra as a 'party drug'," Weinstein said at the time.

Viagra appeared on the market in 1998 and has since earned Pfizer billions of dollars in sales.

But despite being the world's biggest drugmaker in terms of revenues, Pfizer is currently suffering as generic drugmakers pump out rivals to some of its best-selling medications and on Monday unveiled 10,000 job cuts.