LONDON (AP) — Britain's unelected House of Lords on Monday dealt a strong defeat to the government of Prime Minister David Cameron by voting to delay a cut in tax credits.

The 307 to 277 vote in favor of halting the cuts puts the House of Lords in a rare clash with the House of Commons, which backed the measure supported by Cameron and his ministers as part of the deficit reduction plan.

The cuts would affect tax credits for parents and people in low-income jobs. The Labour Party and a number of Conservative lawmakers oppose the cuts arguing that backing the measure would weaken the party's claim to represent working people.

After an emotional debate, the House of Lords took the unusual step of refusing to back a Commons' vote involving fiscal matters. The Lords traditionally let the lower House of Commons' position on finances stand.

In the House of Commons, Conservative Party lawmaker Edward Leigh said the rights of legislators are being trampled by the unelected Lords.

"Not for 100 years has the House of Lords defied this elected House," he said after the Lords' vote tally was announced.

Critics said as many as 3 million people would be worse off under the proposed changes, the latest in a string of government spending cuts that are part of the austerity plan enacted by Cameron and Treasury chief George Osborne.

The government had claimed the cuts will be offset by other measures, including a higher minimum wage.

By tradition, the House of Lords can only revise, and not overturn, legislation passed by the Commons. But the tax-credit changes take the form of new regulations rather than a new law, so members of the Lords asserted they have the power to stop them.

Labour Treasury spokesman John McDonnell had urged the government to do a "U-turn" on the measures to protect British workers.

"These are people who go to work, look after their kids, do everything asked of them and they are going to lose, on average, about 1,300 pounds ($2,000) a year," he said.

Cameron insisted this week that the cuts were necessary.