In my view, that balance is obtained through trust and confidence. The parliamentary system is based on confidence. If the House has confidence in the government, there are times when the House will take the government's word for things. The theory is, once you lose confidence and you don't trust the government anymore, you vote against it and you go for an election.
Somewhere in between those extremes there is the situation where members of the House may have reservations about the veracity of what the government is saying. Arguably it's within the government's control as to whether it is believed or not believed, depending on whether what it says is credible or not over time. Every government faces that task of maintaining its credibility, yet at the same time not disclosing information of a kind that should not be disclosed.