cobblers!
Cobblers is Cockney Rhyming Slang - it's an insulting term declaring that something is rubbish or worthless. It is the shortened form of cobbler's awls, rhyming with balls (as in testicles, not round things people play with...er, hang on a minute...OK, maybe they do but you all know what I mean!).
An awl, is a pointed tool for making holes in leather by the way.