Shadow Chancellor Alan Johnson says Osborne's Spending Review amounts to a "reckless gamble with people's livelihoods" and accused the government of being motivated by ideological reasons.
Johnson said although spending reductions are needed to reduce the deficit, the cuts outlined today risk stalling the recovery.
"The deficit has to be paid down, but today's reckless gamble with people's livelihoods runs the risk of stifling the economy."
He added: "In the context of deficit reduction, speed kills."
He went on to slam the government for "perpetuating a series of myths" to justify its policies and said the Tories are motivated by ideology alone.
Referring to the "deepest cuts in living memory" unveiled by the Chancellor he said: "For some members opposite (the government) this is their ideological objective - this is what they came into politics for."
He blasted the government for exaggerating the extent of the deficit, labelling Tory ministers "deficit deceivers".
"They peddled a whole series of myths to the British public," he said.
He rejected Osborne's claim the government has brought Britain back from the "brink of bankruptcy", pointing out the country had the second lowest debt of any G7 country when the financial crisis hit.
Johnson also claimed Osborne had over-played the amount of interest the UK pays on its debt, saying its debt interest payments have actually been falling since the start of the year.
The newly-appointed Shadow Chancellor accused Osborne of being a political opportunist.
"When the last spending review took place in 2007 he was calling for reduced public spending and regulation of the banking industry and argued we were spending too little.
"In 2007, rather than calling for the regulation banks, he was calling for deregulation."
Finally, he pointed out that neither Scotland, Northern Ireland or Wales had lent their support to the cuts.
"Is this why he calls himself a one-nation Tory?"
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