Millions of poorer families could lose up to £500 a year if Chancellor Jeremy Hunt 'moves the goalposts' for benefits rises, poverty campaigners have warned.

Most at risk are Universal Credit and Child Benefit, as these do not have the same triple-lock protection as pensions. Mr Hunt is expected to announce some rise in benefits as part of a package of measures in this week's Autumn Statement, but fears are growing that the Government may change the way increases are determined in a bid to cut costs.

Working-age benefits normally go up in line with the September inflation figure, which was 6.7%, to maintain living standards. But the Treasury may instead use October's much lower figure of 4.6%, which would save £3bn a year from April, according to the Institute for Fiscal Studies think-tank.

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But according to Louise Murphy, economist at the Resolution Foundation, that would amount to 'moving the goalposts'. She says the average annual income loss for 9m families affected by benefit cuts would be £142, though a working family with three children could lose about £500, according to This Is Money.

In an interview with the BBC, Mr Hunt refused to rule out cutting inheritance and business taxes this week, although it is It is thought his decision will depend on the latest predictions from the UK's main economic forecaster as a Treasury source said no final decisions had been made.

Although Mr Hunt did not deny reports that the Government is considering using October's inflation figure to uprate benefits, he said the Government would be "compassionate" and the the welfare system needed to be reformed "because we believe that making work pay is a vital part of our economic success".

"The Chancellor hopes savings on welfare spending will encourage more people back to work and ease labour shortages," said Lizzy Galbraith, political economist at wealth manager Abrdn. "But clamping down on benefits while announcing a move such as an inheritance tax cut could be hard to sell to voters."