More than half a million people on low incomes missed out on a government grant to help with soaring energy bills.
Earlier this year ministers announced a series of measures to ease the pressure on people struggling to pay their gas and electricity bills.
Among the package, announced by former prime minister Boris Johnson in July, was a payment of £326 – the first half of a total £650 – for millions of people claiming Universal Credit.
But 551,000 people did not get the payment because they earned too much from work, according to analysis by the Labour Party.
The Department for Work and Pensions did not dispute the figures.
Labour says some of the claimants may have missed out because they received two days of pay in the same 30-day qualifying period because their wages come every four weeks.
This meant that their income was temporarily too high and they were there no longer eligible for the cash.
According to Labour’s figures, first reported by the Mirror, a further 6,600 UC claimants were refused the grant because they got a benefits sanction.
Jon Ashworth, the shadow work and pensions secretary, told the Mirror it was “staggering” that people had missed out due to “the quirks of the DWP computers system or sanctions”.
He called on ministers to make sure help got to households that were most in need.
A DWP spokesperson said: “Cost of Living Payments have been designed to target support for households with low incomes, on means-tested benefits.
“But inevitably a small number will be ineligible on the qualification dates of a change of income, earnings or other circumstances.
“All claimants have the right to appeal their entitlement.”