The UK Government's insistence that its benefit changes will help people into work is a myth, according to the Deputy First Minister.
Westminster's welfare reform agenda is actually about making life harder for low-paid working families, Nicola Sturgeon said.
The perception that welfare reforms will sort "the strivers from the so-called scroungers who are feckless, workshy and languishing in their bed all day" is unfounded, Ms Sturgeon told Holyrood's Welfare Reform Committee.
A proposed 1% cap on benefits will hit nearly a third of Scottish households and amount to a 4% cut in income, she said.
The UK Welfare Benefits Uprating Bill will cost Scottish households £210 million on top of £2.5 billion in reductions already set out by the Department for Work and Pensions (DWP), according to the Scottish Government.
Ms Sturgeon said 100,000 Scottish families were affected by child benefit reforms rolled out on Monday. She has commissioned an Expert Working Group on Welfare to firstly design a benefits system for an independent Scotland after 2014 and secondly help mitigate the more pressing UK welfare reforms.
A Department for Work and Pensions spokeswoman said: "In difficult economic times, we've protected the benefits of disabled people and pensioners who have little means to increase their income.
"We've also committed to helping people who claim working-age benefits and tax credits, and will increase this support by 1%.
"This was a tough decision but it will ensure that the welfare budget is sustainable over the longer term and will continue to help the people who need it most.
"The introduction of Universal Credit will ensure that work always pays and will make three million households better off."