When does a joke become a smear?

Paul Waugh highlights a passage from Harriet Harman’s speech today:

“Contrasting Labour’s record on equalities and feminism with that of the Tories, she said that David Cameron would extend foxhunting rights to everyone, while George Osborne would replace a SureStart in every community with ‘a lapdancing club in every community’.”

Now, Paul reports that Harman’s people are saying the “lapdancing” bit is merely a “jokey reference to lapdancing club tickets distributed during last year’s Tory conference in Birmingham”.  But it seems to me that this is a particularly contrived and even nasty attempt to sully an opponent’s name.  I expect the Tories can expect more of this dubious treatment as Brown’s government fight for their political survival.