Gordon Brown has insisted that higher borrowing to shore up the economy was the "responsible" thing to do.
After criticism from economists of the Government's plan to spend its way out of the downturn, the Prime Minister said debt could not be brought down until tax revenues recover.
Speaking at Imperial College in London, he said the only way for Britain to benefit from the "new global age" was to invest in the necessary long-term decisions.
Now was the wrong time to slash investment in areas like education, training, energy efficiency or tax cuts for hard-pressed families, the premier said.
"That means that the responsible course of government is to invest at this time to speed up the economic activity," he said.
"As economic activity rises, as tax revenues recover then you would want borrowing to be a lower share of your national income.
"But the responsible course at the moment is to use the investments that are necessary, and to continue them, and to help people through very difficult times.
"I think that's a very fundamental part of what we are doing."
His comments came after a group of senior economists on Sunday urged tax cuts.
They slated the Government's plans to pour tens of billions of pounds into the economy in an attempt to head off the worst of the turmoil as "misguided and discredited".
