Survey points to effect of overall cut in value of benefits as well as changes to housing benefit and council tax support

The coalition's welfare cuts have pushed 1.75 million of the UK's poorest households deeper into poverty, leaving more families struggling to cover food and energy bills, according to a report.

The report by Oxfam and the New Policy Institute highlights a drop in the overall value of benefits, which rose by less than inflation, as well as changes to housing benefit and council tax support that have forced some families into paying housing costs they were previously deemed too poor to pay.

It finds that together those changes mean about 1.75 million of the poorest families have seen an absolute cut in their income in the past three years.

The report warns that the shape of welfare support has changed dramatically just as people have struggled with rising living costs, and that many jobseekers, carers, single parents and those with disabilities unable to work have become worse off.

"We are already seeing people turning to food banks and struggling with rent, council tax, childcare and travel costs to job centres," says Oxfam chief executive Mark Goldring. "At a time when the five richest families in the UK have the same wealth as the bottom 20% of the population it is unacceptable that the poorest are paying such a heavy price."

The report found that 300,000 households have experienced a cut in housing benefit, 920,000 a reduction in council tax support and 480,000 a cut in both.

In the past year 400,000 households have been pushed further into poverty by cuts to housing benefit or council tax support and households affected by both of those cuts typically lose about £18 per week.

The report follows figures last week that suggested that more than a million Britons have been helped by food banks in the past year.

The Trussell Trust, the UK's biggest food bank network, revealed that more than 900,000 people received food parcels in 2013-14, a 163% increase on the previous year. Its figures understated the likely level of people going hungry, it said.

Oxfam is urging the government to determine what the absolute minimum level of support should be for households. "It must be high enough to mean that those reliant upon it are not forced to walk the breadline," said the charity.

The Department for Work and Pensions said it was making the welfare system "fair to claimants and taxpayers" and insisted a strong safety net remained.