Thirteen million families will lose an average of £260 each year because of the change to working-age benefits, the Institute for Fiscal Studies (IFS) has said.
Reacting to the first all-Conservative Budget in 19 years, the IFS said it was "regressive" and had taken "much more" from the poor than the rich.
George Osborne earlier defended his Budget, saying it represented a "new contract" for Britain.
The CBI has called the Chancellor's minimum wage increase a "gamble" that risked politicising the process and causing problems for some small businesses.
Director general John Cridland said overall he was pleased with George Osborne's Budget but added that businesses were being put under pressure.
"Overall, sorting the public finances, giving people incentives to work, reducing business costs in taxes: full marks to the Chancellor," he said.
"But this issue of the minimum wage will have caught businesses by surprise. It is a gamble.
"The businesses that will be under the most pressure, paying a significantly higher minimum wage - 6% higher on average every year in this parliament - aren't the same businesses as a whole who will get the benefit from the tax reductions."
Since the Budget, a cascade of analysis has crashed across our screens and squirted ink over our newspapers - much of it missing the point.
This afternoon, the Institute for Fiscal Studies presented a damning analysis of George Osborne's Budget. Here we explain the key points.
The Chancellor's "Living Wage" is considerably lower than the rate the Living Wage Foundation campaigns for but this is still a bold move.