The Prime Minister said the Chancellor's remarks about the Philpott case "were absolutely right".
He said: "I think what George Osborne said was absolutely right.
"He said that Mr Philpott was the one to blame for his crimes and he should be held responsible but what the Chancellor went on to say is we should ask some wider questions about our welfare system - how much it costs and the signals that it sends.
"We do want to make clear that welfare is there to help people who work hard, it shouldn't be there as a lifestyle choice and I think that's entirely legitimate."
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