Duncan Smith voices fears over cuts
The Work and Pensions Secretary said a narrow focus on cuts would only deliver savings in the short term.
In a speech to the Policy Exchange think tank, Mr Duncan Smith said the Government needed a different approach to reform.
"Not just cheese-slicing, but recalibrating whole systems so that you change behaviours, and change the culture that allowed spending to get out of control in the first place," he said.
"This is absolutely critical, and I want to take a moment to explain why. When welfare spending balloons - as it has done - the temptation by successive governments has been to squeeze it back down again.
"But, rather like a balloon, when you squeeze it at one end it will tend to grow at the other. So whilst savings must be made, they must also be sustainable.
"Otherwise, once the public finances are back in order, and the economy grows again, so the bidding war will start once more."
Mr Duncan Smith said the coalition was trying to achieve an "internal culture shift" to focus on the impact policies had on people's lives, rather than how much was being spent.
He highlighted the Work Programme, where private firms are being paid for getting individuals back into employment, as an example of the new approach.
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