DETROIT — And you thought no one knew you were doing your holiday shopping from your work computer.

Not only do they know, but the retail industry has christened the Monday after Thanksgiving as Cyber Monday, because the sales spike that happens that day is now too big to ignore.

More than a third of consumers — 37 percent, or 51.7 million people — said they will use Internet access at work to browse or buy gifts online this holiday season, according to a Shop.org and BizRate Research survey released this week.

A host of online retailers from Godiva.com to QVC.com are creating promotions to drive online shoppers to their Web sites Monday.

About 43 percent of online retailers are offering special deals on Cyber Monday such as free shipping, gifts with purchases and discounts, the survey said.

Most people who shop online at work won't admit it because it may make them appear to be slacking off or, more likely, it's against company policy.

Calls to several companies in the metropolitan Detroit area solicited a uniform "no comment" this week. Many companies did not want to appear unprofessional by even discussing whether their employees shop online at work.

One online shopper who works at a local college said she frequently browses various Web sites from her work computer on her lunch hour or when she has some down time. The worker requested anonymity for fear of being fired.

The survey found that 77 percent of online retailers said their sales increased substantially last year on the Monday after Thanksgiving.

And men were more likely to shop online from work, 42 percent, compared with 32 percent of women.

"Men won't take their buddies to a mall and ask if they chose the right gift, but they will ask their colleagues what they think of a gift they are selecting online," said Lorrie Norrington, of Shopping.com, a comparison-shopping site.

Caryn Klebba, 30, a working mother from Berkley, Mich., said she shops online for the holidays, birthdays and weddings because her schedule is so full. But she usually doesn't have time to do so at work.

"I love to put my son to bed and hop online and do my shopping," Klebba said. "It is all about saving time."

Jim Sluzewski, spokesman for Macy's department store owner Federated Department Stores Inc., said the company has launched new promotions for the holidays to capture the online shopper's attention.

It plans to give away a trip to the Macy's Thanksgiving Day parade in 2006 in New York or $50,000. Shoppers can get a peel-and-win entry in stores and then go online to enter.

He said Macys.com shoppers also will receive free shipping and other special deals.