That is, they often imply that all tax rate cuts or avoidance of increases would pay fully for themselves with increased tax revenue.

FORBES: Lying With Words As Well As Statistics

As you know, George Osborne is scrapping the 50% top rate of tax, and replacing it with a 45% rate, because he was informed by Her Majesty's Revenue and Customs that there was massive avoidance of the new top rate, such that the yield from the higher rate was trivial.

BBC: More than 70% of high earners paid 50% tax rate

It had already committed itself to cutting 4 pence off the basic rate of income tax to be paid for by taxing the rich and clamping down on avoidance scams.

BBC: Challenge for Clegg despite tax victory