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, 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.
Ms Sturgeon updated the committee on her work to ensure welfare reforms do not impact on local services such as disabled parking and free school meals that are built on existing UK entitlements, known as "passported benefits".
Conservative MSP Alex Johnstone, the only committee member from a UK coalition party, sought an assurance that passported benefit updates will not detract from the UK Government's aim "to make work pay and reduce benefit claims".
Ms Sturgeon said: "This myth that these changes are all going to be felt by people who are feckless, workshy and languishing in their bed all day: the impact of welfare reform will fall on a significant amount of people who are in work and striving really hard to provide a decent standard of living for their kids.
"Changes to child tax credits, working tax credit and the benefit uprating mean they are going to find that a lot harder. This is not the distinction between the strivers and the so-called scroungers that the UK Government seems to want to think it is. This is actually about the UK Government, in many of these changes, making life harder for people who are working very hard already."