A legal research company said Thursday it will greatly restrict customer access to Social Security (search) numbers in response to complaints from Congress that its previous policy of limited sales of the numbers invited identity theft.

Westlaw, a Minnesota-based legal research firm, said private companies and many government offices no longer will be able to obtain such information from the company.

"The events of the past months illustrate the importance of tougher controls, and we're pleased to be a part of a broader and ongoing effort that supports both individual privacy and homeland security concerns," said Peter Warwick, CEO of Thomson West (search), which operates the online Westlaw service.

The company's practices came under fire from lawmakers after another data company, ChoicePoint (search), announced some 145,000 customers had been exposed to identity theft.

Westlaw has not suffered a similar breach, but Sen. Charles Schumer, D-N.Y., called on the company to tighten restrictions on the information available to customers in the wake of the ChoicePoint problem.

Under the new policy, about 85 percent of Westlaw customers who previously had access to the Social Security number search will no longer have such access.

All private companies, and many government offices, including the U.S. Senate, will no longer have access to Social Security numbers through Westlaw. Access will remain for some law enforcement agencies.

Congress has stepped up pressure on data companies that collect huge amounts of private information.

On Tuesday, ChoicePoint CEO Derek Smith appeared before a House Energy and Commerce Committee panel to publicly apologize to customers whose information may have been obtained surreptitiously.

Appearing beside him was LexisNexis CEO Kurt Sanford, whose company also had a breach involving information on about 32,000 people.

The two executives said they would support some proposals to toughen laws governing consumer privacy.

They did not support a more sweeping prohibition on the sale of Social Security numbers, arguing such sales may be necessary for law enforcement or debt collection.