The gender gap has widened when it comes to hygiene, according to the latest stakeout by the "hand washing police."

The gender gap has widened when it comes to hygiene, according to the latest stakeout by the "hand washing police." One-third of men didn't bother to wash after using the bathroom, compared with 12 percent of women, said the researchers who spy on people in public restrooms. They reported their latest findings Monday at a meeting of infectious disease scientists.

Two years ago, the last time the survey was done, only one-quarter of men didn't wash, compared with 10 percent of women.

"Guys need to step up to the sink," said Brian Sansoni, spokesman for the Soap and Detergent Association, which co-sponsors the survey and related education campaigns.

The latest findings were based on observations last month of more than 6,000 people in four big cities.

Frequent hand washing is the single best thing people can do to avoid getting sick, from colds and the flu to germs lurking in food, doctors say. And a recent Harris Interactive survey found 92 percent of Americans said they always wash up after using the bathroom.

But researchers for the American Society for Microbiology found that only 77 percent actually do, when it comes to public restrooms. That's a 6 percent decline from a similar study in 2005.

Nearly three-fourths of Americans said they always wash up after changing a diaper, 78 percent said they do so after handling or eating food; 42 percent after petting a dog or cat, 25 percent after handling money, and 34 percent after coughing or sneezing.