TORY cuts to tax credits were branded “morally indefensible” last night amid a constitutional showdown between the government and Lords.

Cutting the benefit that keeps low-wage workers out of poverty will see 3.3 million families lose £1,300 a year from April.

A Labour amendment effectively killing off the policy as it stands was expected to be carried in the Lords, where the Tories do not have a majority.

But in a desperate bid to defeat the motion, government whips hauled in every Tory peer available, including composer Andrew Lloyd Webber.

The constitutionally unprecedented attempt by the Lords to block a government spending measure was one of the most damaging moments for David Cameron during his five years in Downing Street.

Peers were free to throw out the cut because the Tories did not include the unpopular policy in their general election manifesto.

Mr Cameron had even promised in a pre-election TV debate that he would not cut tax credits.

Labour’s Lady Hollis urged peers to protect families “who trusted the Prime Minister’s word that tax credits would not be cut and trusted Parliament when we said we would make work pay.”

In the stand-out speech of an emotive debate, she read aloud four messages from families set to be affected by the cut.

One testimony was from Rachel in Milton Keynes, who is set to lose £2,005 a year and said: “It probably means we will skip a few extra meals to ensure that the children eat.”

The bishop of Portsmouth, moving a “motion of regret” over the cut, blasted the government’s proposals as “morally indefensible.”

The cut will leave 67 per cent of low-waged workers worse-off by 2020, an analysis by Policy in Practice found.

“The government wants people to work, but this goes against that,” it states.

If passed, the Labour motion would delay the government’s proposal for up to three years until protections for current claimants have been introduced, although the cut would still apply to new claimants.

A separate Lib Dem motion throwing tax credit cuts out of Parliament altogether was expected to be rejected.

The Prime Minister has also threatened to appoint 100 new Tory peers to push the cut through the upper house.

The “frankly scandalous” move would cost the taxpayer £2.6 million a year in expenses, the Electoral Reform Society said.

Chancellor George Osborne now faces an uncomfortable time at Treasury questions today in the Commons, where eight Tory MPs have backed a motion opposing the cuts.