Around 2.4 million families in England face an average hike in their council tax bills of £138 next week, according to an anti-poverty charity.
The Joseph Rowntree Foundation (JRF) found abolishing council tax benefit will leave 150,000 families paying an average £300 more a year, while 1.9 million claimants that do not pay anything now will have to pay an average of £140 per year.
The benefit is being replaced by a new system, council tax support, which is run by English local authorities but on 10% less funding.
The Scottish and Welsh governments are making up the cut in their nations, while Northern Ireland operates a different system.
Pensioners are protected under the reforms, but working-age claimants will bear the brunt of the cuts, according to the JRF.
The report found 232 local authorities have devised schemes that will demand council tax from everyone, regardless of income. Just 58 will retain current levels of support for families.
Chris Goulden, head of poverty at JRF, says: "Some of the country's poorest families must find £140 extra from their strained household budgets to pay council tax for the first time.
"This tax hike will push people into poverty or cause more hardship for already very poor households, taking money from families who had little to start with."
A spokeswoman for the Department for Communities and Local Government says: "Council tax benefit spending doubled under Labour and welfare reform is vital to tackle the deficit that we inherited.
"The localisation of council tax benefit will give councils stronger incentives to cut fraud, promote local enterprise and get people back into work."