The Children’s Society, a charity that works with vulnerable youngsters, warned tough welfare policies would hit millions of low-income families across the UK and "push many more children into poverty".
Laws that will come into effect this April will see child tax credits, working tax credits and job seekers' allowance frozen - rather than rising in line with inflation and living costs - something charity chiefs say will mean parents could lose up to 12% from the real value of their benefits by 2020.
The tax measures, which have been announced but not introduced, and are due to be debated by MPs on Tuesday.
While some changes, such as the introduction of a higher minimum wage, might increase household incomes by 2020, others will cancel out any gains by significantly cutting key support for many families, a report from the Children's Society said.
The research claimed young parents and families with disabled children claiming Universal Credit for the first time are particularly likely to lose out.
Chief executive of the Children's Society Matthew Reed said the government's austerity agenda would drive more children into poverty and called on George Osborne to protect youngsters from future cuts.
“Families on low incomes are facing a barrage of cuts. If ministers are genuinely concerned about child poverty they must reconsider plans to freeze benefits over the next four years," he said.
"At the very least, the Government needs to guarantee there will be no further cuts when the Chancellor delivers his Budget next month.
“Austerity has hit families hard, including those in work. Further cuts to support would push more children into poverty and undermine incentives for families to move into work or earn more.”
Impact on different families highlighted in today's report
- A 23-year-old primary school teacher and single mum of two children renting their home could be worse off by £239 per month (£2,868 per year)
- A nurse and her partner with three children, renting in London, could be worse off by £425 per month (£5,100 per year)
- An army corporal and his partner with three children, including one who is disabled, who own their home, could be worse off by £771 per month (£9,252 per year)
Iain Duncan Smith's Department for Work and Pensions, which drove through the reforms to cuts and freezes to families' benefits, said the measures had been taken to bring spending "under control".
“Our welfare reforms are crucial to delivering a higher-wage, lower-tax, lower-welfare economy and thus ensuring that the most vulnerable are always supported and that work always pays for those that can work," a spokesman said.
“We are bringing welfare spending under control, while – crucially – helping people into work and, through Universal Credit, helping them to earn more.
“More people than ever before are now in work, wages are rising above inflation, and the National Living Wage is set to boost pay even further.“