Coalition Says no to openness

How many times are the Coalition going to change the reason for not wanting Treasury to cost their polices. So far we have had:-
- We have adequate costing done by a Third Party.
- We don't trust Treasury (what will happen if they win?)
- They are confidential and breaks the Westminster system (what??? how)

We need much more open Government - the coalition seem to want continue along the way it alway has.