New York, Dec. 20 (Reuters): The holiday season brings festive parties, family gatherings — and a deluge of spam.

Unsolicited messages, or spam, which account for nine out of 10 emails, fill up the inboxes of computer users more than ever at this time of year, experts say.

“Every year we see a seasonal increase around the holiday season. It’s just worse than it’s ever been before this year,” said Daniel Druker, executive vice-president of marketing at Postini, a company that provides message security services.

Spammers spew out millions of emails. Some hawk pharmaceuticals and sexual aids, others offer hot stock tips. The unscrupulous commit identity theft by luring unsuspecting recipients into disclosing personal information, while others commit fraud with the lure of phoney offers.

The glut of spam can clog business communications systems to the extent that emails at the workplace can be held up for hours, experts say. “The threat of this is that email becomes no longer productive as a tool, and that is scary because email is ubiquitous. Most businesses could no longer run without it,” Druker said.

Spam cost an estimated $17 billion in the US last year in lost productivity and the expense of measures to fight it, according to San Francisco-based Ferris Research. Worldwide, the cost was estimated at $50 billion.