Why is Gordon Brown such a liar?

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Today's interview in the Guardian contains the same old lie on Tory cuts.

The Tories have made, for them, a cardinal mistake in that they admitted the truth - that if you take 10% off the health service or schools or policing, you've cut into the jobs, the services, the expectations.

Now we all know that these are based on Labour's own figures and so if the Tories are cutting so are Labour. But the 10% cut figure came about because the Tories are going to protect NHS funding and Labour will not. So if the Tories are protecting the NHS budget, why does Gordon say that 10% could be coming off the NHS budget?

What could have happened in his past to make him such a liar, a deceptor?