Labour leader Ed Miliband has dismissed claims there is a £27.9 billion "black hole" in his party's spending plans as "nonsense".
Treasury minister Sajid Javid released an analysis by Treasury officials which he said showed Labour promises would require more than £1,000 extra borrowing per household in 2015.
But Mr Miliband insisted Labour would not increase borrowing to fund day to day spending in its first year of power if the party wins the next election.
He told BBC 1's Andrew Marr Show: "Let me be clear, we have said in 2015/16 that Labour won't be borrowing more for day to day spending.
"We have been absolutely clear about that. The next Labour government will be facing different circumstances from the last.
"Ed Balls and I have both said times are going to be tough and frankly I think Treasury ministers should be worrying about the cost of living crisis facing families and not making up things about the Labour party."
Speaking in Brighton, where Labour is holding its party conference, Mr Miliband said he wanted to reduce low-skill immigration and insisted the party was committed to introducing an immigration bill in its first year of office.
Labour plans to force firms to train a British apprentice for every non-EU overseas worker they bring to the UK to help create a "high wage economy" and ease the cost of living "crisis".
"In our first year in office we will legislate for an immigration bill which has secure control of our borders, cracks down on exploitation of workers coming here undercutting workers already here, and says to big companies that bring in people from outside the EU that they can do that, within a cap, but they have got to train the next generation," he said.
"I think that's the right approach. Why is that so important? It's about making our economy really work for working people in our country and training up our people, that is the way to tackle our standards of living issues that so many families are facing in this country. I do want to get low skill immigration down and therefore overall immigration down, yes."