Department of Commerce officials tried to block congressional investigators from speaking with whistleblowers claiming U.S. Census Bureau records were being fabricated, according to a report by House Republicans to be released Thursday.

“Commerce Department officials showed up uninvited to a transcribed interview with a Census Bureau employee and put her in a position where she was forced to risk retaliation if she excluded them from the interview,” according to a joint report by the House Committee on Government Oversight and the Joint Economic Committee of Congress.

“The Commerce Department officials who ambushed the witness claimed that congressional staff may only speak to witnesses in the presence of department personnel, and that it is unlawful for congressional staff to speak with department employees directly.”

In fact, the committees noted, federal law guarantees that the right “to furnish information to either House of Congress, or to a committee or member thereof, may not be interfered with or denied.”

The Commerce Department did not respond to a request for its version of events.

The committees' inquiries were prompted by a New York Post story that said that Census employees were fabricating data to mislead the public about the employment rate for political purposes.

The investigators found no evidence to support that allegation, except that a few Census employees had fudged the numbers to make quota.

The committees issued recommendations on ensuring that Census data is reliable in spite of incentives to garner responses at all costs.

On Thursday, Census Bureau Director John Thompson and the Commerce Department's inspector general will testify on the findings at a hearing of the oversight panel's subcommittee on the federal workforce, the U.S. Postal Service and the Census.