Bastardeux,
I'm afraid you're the one that's confused. The coalition was attempting to halve the national
annual deficit, from £160 Bn odd a year down to something like £80 Bn a year. See the first graph in this article for recent annual deficits:
Deficit, national debt and government borrowing - how has it changed since 1946? | News | guardian.co.uk
However, even if they had achieved that, then over 5 years the national debt would have gone up by say £160Bn + £130Bn + £110Bn + £95Bn + £80 Bn. They won't even manage that, the situation is worse than planned and all the while the
national debt continues to rack up:
UK National Debt - Economics Blog
It's current about £1,145 Bn and rising every year:
UK National Debt Clock - No-nonsense Guide to Britain's Debt Crisis
The coalition had no ambitions to halve the national debt, that would have been impossible!! That would require us to have annual budget surpluses and pay off some of the national debt!!
With regard to the national debt, the major economic issue is what percentage of GDP it represents, most countries owe say 40% of their GDP, when that figure rises significantly markets get very twitchy, and borrowing becomes very expensive. The coalition might well have been attempting to reduce the growth of the national debt (by bringing down annual deficits), while hopefully expanding the size of the economy so that the overall debt when measured as a % of GDP decreased, even though the actual size of the debt had still increased!! However, their main stated aim was halving the annual deficit!!