The difference between 'deficit' and 'debt'

'Debt is owning the bank money.
Deficit is earning £100 a week and spending £200 a week.
So when Brown saying reduce the deficit by half he means we'll be spending £150 a week, even though our income is only £100 still.
So, under Gordon Brown our debt will increase - until we can no longer borrow money and the proverbial hits the fan.'

The excellent definition offered by 'GDT' in the comments to Fraser Nelson's Spectator piece entitled 'Why Cameron must never say "deficit".'

Read the whole article and the comments, there is much sense there.