Via Twitter @Oleuanna has asked about this post and the underlying concepts; my answer as it got to long is here for your consideration/ridicule:
Oleuanna the answer is a complicated one & I would never do it justice; in a nutshell governments have several ways of raising money other than direct taxation - in this case they "sell debt"; essentially a govt. bond is a promisory note of a return on it paid out of taxation - money you thought was going to paying for a service actually goes to paying off money they borrowed to pay for it in the past.
Essentially they are paying for the present with our future.
In practice we all do this; debt can be a useful thing for deferring costs till you can afford them; Labour though have taken the piss quite seriously in that they've essentially maxed out the credit card and the bailiffs are now aknocking.
The "structural deficit" everyone keeps going on about is the percentage of spending on public services that is not covered by tax receipts, ergo by NuLabours Bond sales/Credit thing rinse; we are just racking up debt as we go and it would take 75% of GDP in one year to pay back this debt instantly.
For a better idea of how this scam has worked see this post at BOM, a brilliant resource for all things fiscal in govt., otherwise look up LPUK's fiscal policy for a more indepth idea of what's at stake. Lastly for fun go to YouTube and search the term "money as debt"; you'll get some interesting results.