The 223-193 vote in favor of blocking the new overtime rules defied the White House, which has threatened to veto a massive spending bill now on the House floor if it contains any language tampering with the rules that took effect Aug. 23.
Democrats, united against the rules, were joined by some 20 Republicans in voting for the amendment to a $142.5 billion health and education spending bill.
The vote was President Bush's second election-season defeat in Congress in two days. On Wednesday the Senate disregarded a White House veto threat and voted to prohibit Mr. Bush from giving federal immigration jobs to private workers.
"The administration has chosen this time to institute new regulations which for the first time in 80 years scale back workers' entitlement to overtime pay," said Rep. David Obey, D-Wis., a sponsor of the overtime proposal.
Democrats sought to depict the issue as an election-season example of the Bush administration's insensitivity to worker rights, saying the overtime privileges of up to 6 million workers were at risk.
The White House and most Republicans insisted the new rules would update an antiquated overtime pay system and would add more than 1 million lower-paid workers to those eligible for overtime.
"I do think that the clarity that comes with these new rules will help better protect American workers," said Rep. John Boehner, R-Ohio, chairman of the House Education and the Workforce Committee.
It was unclear how much impact the House vote would have on the Labor Department rules, the biggest overhaul of overtime regulations in more than half a century. The Senate has yet to take up the health and education bill and the provision could still be stripped out of the final bill when the two chambers, both controlled by Republicans, meet to settle on a final version.
The bill may not reach the president's desk for a possible veto before the election.
Democrats and pro-labor Republicans have fought for more than a year to stop the Labor Department from going ahead with the proposed rules, which the administration said were needed to adjust to changing working conditions and clear up confusion that has led to lawsuits against employers.
"For those who receive overtime it's as high as 20 or 25 percent of their income," said Rep. George Miller, D-Calif., co-sponsor of the provision with Obey. "It's the largest government-imposed pay cut in the history of this country."
The AFL-CIO, which has lobbied against the new rules, said the 6 million workers facing weakened overtime protections include working foremen and assistant managers, nurses, workers in the financial services industry, journalists and others performing small amounts of administrative work.
The Labor Department strongly disputes those estimates, saying 1.3 million workers who earn less than $23,660 a year would become eligible, while about 107,000 white-collar workers making $100,000 or more could lose eligibility.
The Department's solicitor, Howard M. Radzely, said in a letter Thursday that the old rules ceased to exist on Aug. 23 and the Obey-Miller amendment "will essentially serve only to prevent the department from using its enforcement resources to protect the overtime rights of any employee who earns $455 or more per week."
Obey disputed that conclusion, saying the administration has the legal authority to reimpose the old regulations within a day after the new rules are voided.
Congress has debated the overtime issue for more than a year, and last May the Senate, by a 52-47 vote on a different bill, approved language stating that no worker who currently qualifies for overtime should lose that eligibility.
"It just seems to me that the Labor Department, the White House and the Congress should not be complicit in the effort of employers to chisel workers of overtime pay," Obey said as debate on the amendment began Thursday.
The Obey-Miller language blocks all aspects of the rules except those that extend overtime to lower-paid workers.