Osborne's four-year plan cuts spending for services, welfare, the military and elsewhere, while extending the retirement age to 66 for many workers, The Daily Telegraph reported.
"I have chosen in part to pay for that (cuts) by trying to curb the rise in the benefits bill," Osborne said. "That has involved some hard choices but I think they are fair choices. We have got to put the welfare state on a sustainable footing."
A report by The Institute for Fiscal Studies warned Great Britain's deficit could be larger than expected, and said Osborne's budget-cutting efforts should be examined after two years.
In an interview with BBC radio, Osborne said he would stick with the plan he has set out.
"People say 'Where's your plan B?'" Osborne said. I've got a Plan A, which is a pretty good situation. We've got the plan … the country needs a decisive plan."
Osborne said he made a "conscious choice" to protect spending on health and schools, and that forced him to cut welfare spending by more than $20 billion by 2015, the report said.