Shadow Chancellor Alan Johnson has denounced spending cuts plans as a "reckless gamble with people's livelihoods".
Responding to George Osborne's Spending Review, he accused ministers of "throwing people out of work".
He said he agreed the deficit had to be reduced but said the government's plans risked "stifling the fragile recovery".
And he said the poorest would bear a greater burden than the richest, questioning whether they were "fair".
Chancellor George Osborne has laid out the biggest spending cuts since World War Two - including a further £7bn from welfare and a rise in the state pension age - and an average of 19% cuts to departmental budgets over four years.
He argued that the coalition government had rescued Britain "from the brink of bankruptcy" and said Labour did not have a plan to deal with the record budget deficit they had left behind.
Mr Osborne said if the deficit was not tackled "many more jobs will be in danger in both the public and private sector".
But Mr Johnson, who was made shadow chancellor two weeks ago, accused the government of being "deficit deceivers" who had peddled "myths" to the British public, including that the "biggest global economic crisis since the Great Depression is the fault of the previous government".
If countries around the world had not run up debts to sustain their economies when the crisis hit people would have "lost their jobs, they'd have lost their houses, they would have lost their savings", he said.
Mr Johnson told MPs the spending review was "not about economic necessity, it's about political choices" and said a plan for the recovery must be about growth.
He said the poorest would bear a greater burden from the spending cuts than the richest, that "the middle" would be squeezed further and women would shoulder three quarters of the cuts - questioning whether the review was "progressive or fair".
"Today is the day that abstract figures and spreadsheets turn into people's futures, people's jobs, people's pensions, people's services," he said.
He was jeered by Conservative MPs as he said the deficit "has to be paid down" adding: "Today's reckless gamble with people's livelihoods runs the risk of stifling the fragile recovery."
And he accused them of cheering "the deepest cuts to public spending in living memory" suggesting that for some Conservatives, it was their "ideological objective" and "what they came into politics for".
Mr Johnson said the Conservatives' coalition partners, the Liberal Democrats, had supported the Labour view of spending cuts until they entered government.
The shadow chancellor said putting people out of work would mean a bigger welfare bill and less tax. He suggested that a projected 14,000 job cuts in the Ministry of Justice alone could cost £230m in redundancy costs and pointed to an estimated that there would be 490,000 public sector job losses.
"What will the total redundancy bill be?," he asked.
Labour were looking for a "much more gradual, much slower reduction", he said, adding a "rush to cut the deficit endangers the recovery and reduces the prospects for employment in the short term and for prosperity in the longer term".