The Labour shadow chancellor moved to clarify the party’s position after shadow chief secretary to the Treasury Seema Malhotra and shadow international development secretary Diane Abbott suggested a decision had yet to be taken.
Mr McDonnell tweeted: “We are calling on Osborne to reverse his decision to cut tax credits. If he doesn’t reverse these cuts, we’re making it clear that we will.”
Ms Malhotra was asked repeatedly by Andrew Marr on the BBC yesterday whether her party would reverse the cuts, ahead of a crunch House of Commons vote today.
But she would not commit, simply stating that Labour does not want the cuts to go ahead.
She said: “We have said this cut should not go forward … this is a cut to hard-working families who are doing absolutely the right thing. It is a work penalty.”
Ms Malhotra said Mr Osborne has “no transition plans” for bringing in the cuts which would be a “false economy” as they could lead to people being unable to pay their rent.
Mr Marr asked Ms Malhotra: “To be absolutely clear, Labour would restore the whole lot? Yes or No?” She said: “We don’t believe these cuts should go forward from next April.”
When asked again if she would reverse the planned cuts, she said: “We are saying we don’t want them to go forward now.”
Tax credit cuts will be debated in Parliament today during an opposition day debate. Ms Malhotra said that she believes her party could win that vote. “I believe we can,” she said. “I very much hope that we can.”
Labour has claimed the changes to tax credits could put 71 Tory MPs at risk of losing their seats because of the unpopularity of the policy.
Labour claim the 71 MPs – 21 in marginal seats – all represent constituencies where there are more families who will lose tax credits than was their majority in May.
Ms Abbott also refused to confirm that Labour would reverse the tax credit cuts.
“We will not be dealing with the deficit on the backs of the working poor,” she said.
“We have voted against the tax credits and we are constructing a fiscal mandate which will not involve those cuts to tax credits.”