The average family will be £891 worse off under the coalition's tax hikes and benefit cuts in 2013/14.
Labour's claim, based on Institute for Fiscal Studies figures and calculated in comparison with its own 2010 spending plans, comes on a day when a series of the Conservative and Liberal Democrats' biggest reforms take effect.
The bitterly contested 'bedroom tax' reducing housing benefit payouts for properties with spare bedrooms is being implemented from today.
Deeply divisive NHS changes enshrined in the Health and Social Care Act are also coming into force today, transforming the health service as the coalition finally succeeds in driving through its market-driven reforms.
On top of these changes are the group of tax rises and cuts to tax credits which together leave families £17 a week worse off in the next 12 months.
Cuts to council tax benefit alone will leave 2.4 million families on low incomes paying an average of £138 more council tax this year, the Joseph Rowntree Foundation claims.
The 'bedroom tax' is expected to cost 660,000 people an average of £728 a week.
Further changes coming into force on April 6th, the start of the new tax year, are also being highlighted by Labour.
The top rate of income tax is coming down from 50p to 45p, child benefit will be frozen for a third year and the 'granny tax' will see 3.8 million pensioners lose £3.6 million a year.
"These shocking figures show the huge hit millions of families are facing at the very same time as David Cameron and George Osborne are giving millionaires an average £100,000 tax cut," shadow chancellor Ed Balls said.
"It cannot be right to force millions to pay more while millionaires pay less. This is the week when the whole country will see whose side David Cameron and George Osborne are really on and who is paying the price for their economic failure."
The chancellor and work and pensions secretary Iain Duncan Smith mounted a defence of their changes in a jointly-authored article in today's Telegraph newspaper.
"Labour oppose everything we're doing to clear up the mess, but offer no constructive alternative," the pair complained.
"Ed Miliband's position is controlled by the vested interests of the left – his trade-union paymasters and radical left-wing pressure groups.
"Bringing Labour's soaring benefits bill under control means we have been able to protect spending on the NHS and pensioners, cut the deficit by a third and help working families.
"What we're doing this coming week is making welfare fairer, helping to create jobs, and making sure you can keep more of what you earn."