Working age adults will be hundreds of pounds a year worse off because of Government cuts to welfare, it has been warned.
The Welsh government said Westminster's plans for social security will cost an average of £500 a year for adults in Wales.
In some areas, such as Merthyr Tydfil and Blaenau Gwent, the figure will be as high as £600, it was claimed.
The total annual loss of income for Wales by 2015/16 will be around £930 million, according to research.
The Welsh government also warned there will be a "considerable impact" on the incomes of sick and disabled people in Wales.
Communities minister Jeff Cuthbert said: "Communities across Wales are being hit hard by the changes to welfare. Our latest research shows how decisions being made in Westminster will have a real difference on the money in the pocket of many families with a knock-on effect on their quality of life.
"Some of these cuts are hurting low-income families at the very time they are seeing their incomes squeezed and are struggling to cover their everyday costs.
"The reality is we are going to see many get worse off and the wider economy of many communities will also suffer as people have less money to spend on local services and local shops.
"Within our budgets there is no way the Welsh Government can step in to cover the gaps being created by the dismantling of welfare, but we will continue to do all we can to help the most vulnerable in Wales."
A Department for Work and Pensions spokesman said: "Our welfare reforms will improve the lives of some of the poorest families in our communities, with the Universal Credit making three million households better off, including 200,000 households in Wales who will be better off by an average of £163 per month."