Almost 200,000 unemployed adults will lose around £500 a year if planned housing benefit cuts go ahead, union leaders have warned.
The TUC said some of the most vulnerable people in the country will be hit by proposals for a 10% reduction in the benefit of adults who have been claiming jobseeker's allowance for more than a year.
Disabled workers, lone parents and the recent homeless were among the groups most likely to be affected, said the TUC.
General Secretary Brendan Barber said: "This cut in housing benefit will make a real difference to some of the poorest and most vulnerable adults and families, who will find themselves out of pocket to the tune of nearly £500 a year.
"Long-term unemployment is not a lifestyle choice, it is a debilitating and stressful experience which puts unemployed people and their families at higher risk of poverty, poor health and relationship breakdown.
"The long-term unemployed need help and support to get them back into the labour market. They should not to be blamed for their predicament by having vital benefits cut. This is another example of the Government making struggling families bear the cost of the recession, while the rich have been let off."