A question about salary sacrifice...

[Jonny_]

I was pondering something today, and the thread on salary sacrifice pensions has reminded me.

My pension contributions are made via salary sacrifice, and I lease a car for my fiance via SS too.

What I pondered was, is there any specific reason preventing mortgage payments being made via salary sacrifice? As it's a large and regular expenditure for most of us the tax and NI savings could be significant. I can't be the first person to think this up, is it actually feasible or does something preclude it?