[columbo]

I'm not a fan of "ask you to leave", it sounds more like someone that is too afraid to face up to the decision they are making.

"John, due to reasons X and Y you will no longer be employed with this company."

If I had to choose, I'd rather hear something like that.

[brazzy]

How about "we have decided to end your employment"? Seems the most honest way of putting it to me .

[maratd]

Meh. How about "we're going to have to part ways" ... stress that the situation can't continue, not that you made some decision. Things are simply untenable and that's that.