Chancellor George Osborne has "lurched to the right" and ceded the political centre ground to Labour, Ed Balls said.
Writing in the Guardian, Mr Balls wrote that Labour was committed to eradicating the deficit but argued that the Chancellor had lurched to the extreme by proposing drastic shrinkage of public spending.
It comes after Tony Blair suggested in an interview with the Economist that Labour had strayed from the centre ground.
The shadow chancellor wrote: "Let me be clear, including to those who would wish it were not so: Labour will need to cut public spending in the next parliament to balance the books.
"But Ed Miliband and I do not believe a 35% state can be sustained without causing huge damage to our NHS, policing, defence, local services and economic infrastructure."
Mr Balls said Mr Osborne's "increasingly extreme and ideological approach" went "far beyond the necessary task of deficit reduction".
"It is a risky second-term Conservative project to shrink the state - a lurch to the right which has left Labour as the centre-ground alternative," he wrote.
"So the economic choice at the election is now stark and clear. Do we adopt a Labour plan to change our economy, so that it works for working people again and to get the deficit down in a tough and balanced way?
"Or do we carry on with the same failed Tory policies and slash public services to a level of national income last seen in the 1930s?".