Leslie made his comments in the wake of the 2014 Budget, in which the Chancellor announced that the deficit will come down by half in the coming year.
He said: “George Osborne will be disappointed that he borrowed more last month than the same month last year. His promise to balance the books by next year now lies in tatters.
“The Budget revealed borrowing is now forecast to be £190bn more than planned under this government. This is the cost of the three damaging years of flatlining and falling living standards we have seen since the election.”
The UK’s tax deal with Switzerland is said to have raised a quarter of what was expected, making just £4m last month.
Leslie added: “We will get the deficit down in a fairer way, including by reversing David Cameron’s tax cut for the top 1% of earners, and we will act to secure a strong and balanced recovery that delivers rising living standards for the many, not just a few at the top.”