The Tory leader was speaking at the launch of a new campaign featuring a hard-hitting poster.

It features a photograph of a baby and the slogan: “Dad’s nose, mum’s eyes, Gordon Brown’s debt – Labour debt crisis: Every child in Britain is born owing £17,000. They deserve better.”

The poster - which features the child of two Tory supporters - will be shown at 260 billboard sites across the country.

Mr Cameron said that with national debt set to top £1trillion, interest alone amounted to more than was spent on education.

He said: “I think it is an extremely powerful, important and responsible message that we are quite right to get across.

“Labour are getting it wrong. It’s easy for politicians to talk about tax rates and borrowing as if there was no tomorrow, but there is a tomorrow and it is going to be paid for by our children.