What is Labour promising on balancing the books?

The first page of Labour's manifesto is out a bit earlier than the rest. It contains one commitment we're likely to hear heavily debated in the next three and a bit weeks:

"We will get national debt falling and a surplus on the current budget as soon as possible in the next parliament"

Labour is pledging a surplus on the current budget. This means that government revenue should cover day-to-day spending on things other than investment on assets like buildings and roads.

So the government will still be running a deficit — spending more each year than it brings in.

The logic for that, Ed Miliband has argued, is that: "Productive investment in our infrastructure should be seen differently from day to day spending because it often has a greater economic return."

The overall deficit under Labour is likely to be around £30 billion each year when investment is included. That's on the basis that net investment this year is expected to be about £30 billion, and it's forecast to remain at roughly that level over the next parliament. So assuming the surplus Labour plans on the current budget is small, and that no cuts are made to investment spending, that will be roughly the size of the deficit.

How does this fit in with falling debt?

Previously, Labour has stated that their target is actually to have debt falling as a proportion of GDP. We're already forecast to have net debt falling as a proportion of GDP in 2015/16 despite the government running an overall deficit (because the government is selling assets).

But if the economy grows fast enough, then debt as a share of GDP can fall without asset sales, and while the government is running a deficit.

Both Labour and the Conservatives are planning for the debt to fall on this basis after the election while still running a deficit.