The cost of living has been rising more quickly for the poorest households as a result of higher energy and food bills, according to new research.
The TUC said CPI inflation for the poorest tenth of households in February was 4.1%, compared with 3.3% for the richest 10%.
Poorer families have been hit by higher inflation over the past year because they spend a larger proportion of their income on food and utilities, said the union group.
TUC general secretary Brendan Barber said: "People have been getting poorer every month for the last two years as high inflation, tax rises and the dire state of the economy take their toll on family budgets.
"Over the last year the poorest households have suffered more than anyone else from rising food prices and soaring gas and electricity bills. The Chancellor's obsession with raising VAT, along with swingeing cuts to tax credits, has made life even tougher for those on low to medium incomes.
"Consumer spending plays a crucial role in driving our economy so it's in all our interests for people to start getting decent pay rises. But the Government policy of confidence-shattering austerity is having the opposite effect."