Well it's quite easy to give the impression that everything is rosy if you spend like there is no tomorrow, i.e. bribe the electorate in to thinking that funds are unlimited. All those years of fat that the previous Labour government enjoyed, they never put a single penny aside for a rainy day, oh yes, because it was supposed to be end of boom & bust, wasn't it? That didn't turn out too well then did it? So they left a bare cupboard, a mess for someone else to sort out, like they always do.
@bishblaize made a decent point in his post though, Labour overspend and drop the country in the shit, then the Tories are forced to underspend to stop the country going over the precipice, which makes them unpopular because everyone wants something for nothing.