Malingerer

He's not really ill. He's just a malingerer.

Tom is such a malingerer that you can't count on him to get anything done, no matter what promises he makes.

It is telling, in this context of rising rates of mental illness, that New Labour committed itself, early in its third term in government, to removing people from Incapacity Benefit, implying that many, if not most, claimants are malingerers.