“These accounts, coming from the front lines, point a big red arrow at the large problem of taxpayers being stiffed,” said Senator Ron Wyden, Democrat of Oregon, who has been investigating the accusations.

“If it was one isolated instance, you could say that’s somebody who had a bad experience and was frustrated,” Mr. Wyden said. “But when you have three or four professional, nonpolitical, independent auditors all bringing the same message, that is too important to ignore.”

By any measure, the Interior Department under President Bush has placed top priority on increasing oil and gas production in the United States. Under its business-friendly agenda, the department has increased incentives for drilling in risky areas, has speeded approvals for drilling applications and has campaigned to open more coastal areas for oil exploration.

Lawyers who have specialized in lawsuits under the False Claims Act said they had never seen a group of government investigators use the law against their own agency.

“Most whistle-blowers are insiders at a company who spot something that government auditors have missed,” said James Moorman, president of Taxpayers Against Fraud Education Fund, a nonprofit organization supported by lawyers that specializes in the False Claims Act.

“But here you have auditors saying, ‘We did our job, we found the problems and our superiors don’t want to hear about it,’ ’’ Mr. Moorman said. “If it were just one auditor, you could dismiss it. But with four auditors, that’s a pattern of practice.”

In their suits, the auditors contend that they had no choice but to go outside the agency because their supervisors ordered them to “cease work” on five separate investigations and drop their claims.