WASHINGTON (Reuters) - A U.S. government program designed to give the public and policymakers a clear view of how Washington uses federal dollars is riddled with errors and new Trump administration changes threaten to make the problem worse, Senate investigators said on Tuesday.

A 2014 law, the Digital Accountability and Transparency Act, requires federal agencies to submit spending data to be posted on the website USAspending.gov. Last year, those 96 agencies spent nearly $4 trillion.

The Senate Permanent Subcommittee on Investigations found that at least 55 percent of the data submitted during an April-June 2017 review period was inaccurate, incomplete or both.

For example, investigators found that for the Department of Homeland Security, dollar figures on the website for some contracts it awarded did not match up with the actual contracts.

“It is troubling that most federal agencies failed to comply with this law,” said Republican Senator Rob Portman, who chairs the panel. The senior Democrat on the subcommittee, Senator Tom Carper, added in a joint statement that the failure “has diminished the ability of policy-makers and taxpayers to see how their tax dollars are being spent in a timely and accurate way.”

President Donald Trump was elected in 2016 on a promise to “drain the swamp” in Washington. The 45-page report found, however, that last month the Office of Management and Budget and the Treasury Department issued new guidance for the program “that weakens data standards and could lead to continued inaccurate DATA Act submissions.”

The Treasury Department, which is responsible for ensuring that all agencies submit accurate spending data, had one of the worst performance records, according to the report: “Ninety-six percent of the Treasury Department’s own data was inaccurate.”

The Department of Energy outdid Treasury with a 100 percent error rate, investigators found. On the flip side, the Environmental Protection Agency had zero errors during the review period, which covered three months shortly after the Trump administration came into power.