Last year, the Trade Union Congress produced an analysis that estimated that in 2024, 3.8 million people were working an average of 7.2 unpaid hours a week, losing earnings of £8,000 a year.
The authority said those working in teaching and health and care professions were most likely to work unpaid hours.
Finance Minister Lucy Rigby said: “If reform wants people to take their unfunded, trite package plans seriously, they should be clear about where their £40 billion cuts would lie and which public services would pay the price.”
Shadow Chancellor Sir Mel Stride said: “Hard work should be rewarded, which means cutting taxes in a fair and responsible way. The reform proposal does not make any new savings… they continue to promise things they cannot deliver.”
Liberal Democrat deputy leader Daisy Cooper: “Farage’s fantasy economy is a gamble our country cannot afford.”
“The Liberal Democrats are the only party to have seized their opportunity in power to raise the income tax threshold and completely exempt millions of people from paying taxes.”
Helen Miller of the Institute of Fiscal Studies said the reform proposal was “problematic in principle and practice” and “if the intention is to increase labor supply, it is not clear why an incentive should aim to increase the hours of workers who already work at least 40 hours a week”.
Miller said it could also create an incentive to classify more work as “overtime” to reduce tax payments, adding: “The evidence of a similar French policy is not encouraging.”