CIVIL war broke out among Tories over tax credits yesterday as the party’s oldest think tank warned controversial cuts will “harm workers” — and its election chances.

The Bow Group branded Chancellor George Osborne “wrong headed” over his plans to cut the benefit for low wage workers in a new report.

And they admitted that robbing families of up to £3,000 a year will do massive damage to the Tories’ claim to be the “workers’ party.”

Bow Group chair Ben Harris-Quinney said: “It is unclear why a policy that will disproportionately harm workers is being supported by the Conservative Party at a time when the party is keen to claim the title of the workers’ party.

“There is no doubt that the welfare Bill needs to be reduced, but to target those that are most vulnerable trying to transition into work is wrong-headed.”

The group broke ranks with the Chancellor ahead of Labour’s debate over tax credits cuts in Parliament today.

Some 3.2 million families will lose £1,300 a year on average if these cuts come into effect in April 2016.

Shadow Treasury secretary Seema Malhotra said: “This damning report shows how even many Tories are now beginning to understand how socially unfair and economically illiterate the proposed cuts are.”

Labour revealed at the weekend that 71 Tory MPs have majorities smaller than the number of voters that will be harmed by tax credit cuts.

Ms Malhotra said the MPs have a “clear choice” in today’s Commons vote.

“Do they want to support working families in their constituency or do they want to support these unfair cuts?” she said.

“Their constituents will never forgive them if they vote to make them worse off for doing the right thing.”

Fears over a public backlash are fuelling the growing rebellion within the Tory Party against the Chancellor’s cuts.

Mr Harris-Quinney warned: “It is astonishing how quickly support for the cuts in their current form is disappearing within the Conservative Party as public anger grows.”

And Tory London Mayor Boris Johnson also admitted yesterday that “everybody is concerned about something which bears down unfairly on the working poor.”

He urged the Chancellor — a rival for the Tory leadership — to “make sure that hard-working people on low incomes are protected.”

The Bow Group have called for the cuts to tax credits to be phased in over the next five years alongside increases in the minimum wage and tax thresholds.

But the cuts could be stopped in the Lords, with a cross-party group planning to gang up to outnumber Tory peers in a vote next week.

TUC general secretary Frances O’Grady said: “More and more Conservatives are coming out against the Chancellor’s tax credits cuts.

“They are a simply astonishing attack on working people. Even with a higher minimum wage and higher tax threshold, most low-paid families will be much worse off.

“But despite people from his own party urging the Chancellor to think again, he has refused to listen.”