SAN FRANCISCO — Hoping to establish itself as the Internet's least intrusive search engine, Ask.com is empowering people to prevent their search requests from being deposited in data banks.

The new privacy control, called "AskEraser," is scheduled to be unveiled today. When it's turned on, the safeguard purges a user's search requests from www.Ask.com's computers within a few hours.

Industry leader Google Inc. stores personal information for 18 months, as does Microsoft Corp.'s search engine. Yahoo Inc. and Time Warner Inc.'s AOL retain search requests for 13 months.

The feature follows through on a pledge that Oakland, Calif.-based Ask.com made five months ago as it tried to seize the high ground in an escalating debate about how long search engines and other Web sites should hold on to personal information about their users.

"We definitely want to stand out from the other guys," said Doug Leeds, www.Ask.com's senior vice president of product management. "This level of control is unprecedented and unmatched."

Because Ask relies on Google to deliver many of the text-based ad links on its pages, Leeds said some information about search requests and clicks will still end up on Google's computers even when AskEraser is turned on.

Ask.com, which is owned by InterActiveCorp, is counting on its privacy commitment to lure more traffic to its site.

With a 3 percent market share, www.Ask.com is currently the fifth largest U.S. search engine, based on October traffic tracked by the research firm Nielsen Online. Google was by far the largest with a 55 percent share, followed by Yahoo (19 percent), Microsoft (14 percent) and AOL (4 percent).

Among other things, details about search requests help customize online ads aimed at each user's perceived interests — a practice that's drawing more attention from regulators, lawmakers and privacy rights watchdogs.

Search engines insist they vigilantly guard all personal details about their users, but critics worry the stored information could come back to haunt people if the data is subpoenaed in a legal investigation or stolen by hackers.

Other Web sites also are coming under fire for violating privacy rights in pursuit of profits. In a high-profile example, rapidly growing Internet hangout Facebook Inc. last week gave its users the right to turn off a marketing tool that tracks their online activities, after more than 65,000 people signed a petition to protest the tool.

The other major search engines revised their data retention policies this year and now store information for shorter times. Ari Schwartz, deputy director of the Center for Democracy and Technology, hopes AskEraser will pressure them to go further.

"This is a good first step," he said of AskEraser. "We believe people are paying more attention to issues like this."

Google and its chief rivals say they need to log search requests for more than a year to understand their users' preferences and deliver meaningful results as well as target ads.

Leeds said www.Ask.com isn't worried about the tougher privacy controls undermining the quality of its search results.

Maintaining lists of search requests also is supposed to help combat so-called "click fraud" — a tactic that can saddle advertisers with bogus charges for advertising if not detected.