Read his words - Mr Gauke, the Exchequer Secretary to the Treasury, said: "Getting a discount with your plumber by paying cash in hand is something that is a big cost to the Revenue and means others have to pay more in tax."
It's nothing to do with whether the customer chooses to pay by cash or cheque - I pay my window cleaner with cash if I'm in and send him a cheque asap if I'm out, cost to me is the same plus stamp and envelope, cost to him is a considerable percentage of a relatively small fee taken up with bank charges.
It's the implication that he will split the tax he won't have to declare with you if you pay cash.
Difficult to argue with the hypocrisy charge though!
http://order-order.com/2012/07/24/david-gauke-worked-for-tax-avoidance-firm/?tw_p=twt