Changes to welfare could take £1bn out of the Welsh economy with the South Wales Valleys feeling the biggest impact Assembly members have been told.
Communities & Tackling Poverty Minister Huw Lewis claims Merthyr Tydfil, Blaenau Gwent, Neath Port Talbot, Rhondda Cynon Taff and Caerphilly will fall within the 25 worst affected local authorities in Great Britain.
He has highlighted research by the Welsh Government, the Institute for Fiscal Studies (IFS) and Sheffield Hallam University which claims benefit and tax credit cuts will hit Wales even harder than the UK as a whole due to its higher levels of welfare dependency.
It also warns that reform to Disability Living Allowance and Employment and Support Allowance Income could see some disabled people in Wales lose around £4,000 a year.
The Department of Work and Pensions says the Government is committed to supporting disabled people and spends around £50bn a year on disabled people and their services.
A spokesman said: "Hundreds of thousands of disabled adults and children will actually receive more support than now with the combined effect of benefit changes under Universal Credit."