WASHINGTON (AP) -- Budget cuts to the IRS are hampering the agency's efforts to uncover tax cheats, an agency watchdog said Wednesday, and more trims are on the way under legislation approved by a GOP-controlled House panel.

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IRS budget cuts are hurting tax collections because there are fewer agents chasing delinquent taxpayers, according to a report released Wednesday by the Treasury Inspector General for Tax Administration. The IRS budget has been cut by $1.2 billion since 2010.

The House Appropriations Committee approved IRS cuts of $900 million more on Wednesday on a party-line vote. A huge $153 billion measure funding the departments of Labor, Health and Human Services, and Education won initial approval as well.

Enforcement revenue collected by the officers dropped from a high of $3.3 billion in 2012 to $3.0 billion last year, even as the economy improved.

During that time, the number of revenue officers has been cut by nearly a third, to less than 3,000.

"This report dramatically illustrates the long-term effect of IRS budget cuts on the nation's tax system and revenue stream," the IRS said in a statement. "Cutting our resources in these areas means hundreds of millions of taxes go uncollected."

The IRS' overloaded phone system also hung up on more than 8 million taxpayers this filing season and forced millions more to wait on hold for 30 minutes or longer to get help on their returns.

The House Appropriations Committee also proposed big cuts to AmeriCorps, family planning programs, job training and research into health care systems. The measure cuts almost $4 billion from current levels and $15 billion from President Barack Obama's request.

Republicans did manage to carve out small increases for research toward path-breaking cures, special education and community health centers, but "zeroed out" Title X funding for family planning services.

In the Senate, a vote looms Thursday in a showdown over a mammoth bill to fund the Pentagon, military operations overseas and ongoing operations against Islamic extremists. Democrats promise to filibuster the measure in hopes of winning increases to domestic agencies equal to the almost $40 billion increase Republicans want to give to the military.

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