Shadow chancellor John McDonnell has insisted that Labour's plans to borrow to invest in infrastructure would have a "minimal" impact on servicing the national debt.
Mr McDonnell said the projects would pay for themselves via increased employment and tax revenue.
Pressed on how much extra would need to be spent on servicing debt under a Labour government, the shadow chancellor told BBC Radio Four's Today programme: "The type of journalism where you go into an interview and someone asks you a question on a particular figure, to be honest, is a trite form of journalism. That's why we have iPads, and that's why I have advisers, etc."
Mr McDonnell said borrowing was needed to pay for essential infrastructure like increased housebuilding.
He said: "What we would do is ensure that day-to-day spending was not paid for by borrowing. It will be paid for through our tax system, and that means stop the tax give-away to the rich and the corporations.
"That we would only invest for our infrastructure and that investment would pay for itself on the basis of the growth that we would achieve on those. And that's a one-to-one return.
"Because, immediately that infrastructure puts more people back into work, they pay their taxes and as a result of that you are able to cover your costs."
Liberal Democrat leader Sir Vince Cable said: "It's worrying that the shadow chancellor hasn't done his sums. Or perhaps he has done his sums and he realises they're so horrendous that he's unwilling to acknowledge that his version of a Labour government would put the country into financial difficulties.
"We start from a bad position. The Budget warned of increased borrowing, dependent on the 'kindness of strangers'. A Labour government focused on massive nationalisation would make things even worse."