£1.5bn cut to fund new housing?

According to John Denham, the Communities Secretary, on the "Building Britain's Future" website.

An additional £1.5 billion will be invested over the next 2 years to deliver 20,000 new affordable homes, creating 45,000 jobs in the construction and related sectors.

According to Liam Byrne, on the Building Britain's Future" blog,

This involves no new borrowing, no new money - and I'm pleased to confirm that the resources for the announcements in Building Britain's Future - such as the £1.5 billion on building a new generation of social housing - have all been found within existing budgets.

So, if the money has been "found in existing budgets then that must surely mean they've cut £1.5bn from somewhere else.

Something tells me, with the public borrowing the way it is, they don't just happen to have £1.5bn lying around as a small change.

Worth noting too that when initially launched, they said it was going to be £1.2bn but it was still TBD (to be defined). Frankly I reckon they're just making it up as they go along.