The other day I had lunch with UBC Historian Michel Ducharme. I asked him about the argument (previously discussed here and here) that the PBO is contrary to our system of parliamentary government, or that it undermines responsible government.
I have not found those arguments persuasive, but I wanted to talk to someone who can speak from expertise. He kindly gave me a quick remedial course in parliamentary government. The thoughts below are mine--so don't blame Michel if you disagree.
The Canadian system of responsible government has at its core a close connection between the executive power (exercised by ministers through the crown) and the legislative branch (parliament). This connection comes from ministers being members of parliament, either in the House of Commons or the Senate. Ministers must command the support of the majority in the House of Commons. If they do not, they must resign. In this way, ministers (and the executive power they hold) are responsible to the people through the House of Commons. Because of this connection, there cannot be conflict between the executive and legislative branches.
Contrast this with the United States. The Treasury Secretary wants to get a budget passed. The Treasury Secretary is part of the executive, but has no role in the legislature. If the budget isn't passed by the legislature, then there is conflict. For example, the government shuts down like it did in 1995. In Canada's system, this is impossible because the same people control both the executive and legislative branches. In Canada, if a minister cannot be supported by Parliament, s/he is no longer the minister.
This is the essence of responsible government--the minister is responsible to parliament, not to a president or sovereign.
Now, on to the PBO. Does the PBO interfere with this connection of responsibility between minister and parliament?
No. The PBO provides information to all parliamentarians. This information is used by parliamentarians to help decide if they should continue to support the minister. In this way, the PBO is a tool. The PBO no more disrupts the responsibility of the minister to parliament than does a computer or a pencil. Computers and pencils help parliamentarians do a better job in deciding whether to support the minister. So does the PBO.
If, as a counterfactual, the PBO were required to sign off on the budget, then there would be a problem. In this situation, either the minister would now be responsible to the PBO (which usurps the responsibility of ministers to parliament) or the PBO would become a de facto member of the executive (which cannot be, since responsible government requires the executive to be members of parliament). Either way, this would violate important features of responsible government.
However, so long as the role of the PBO is merely informational (as it is now), then all the PBO does is to allow Parliamentarians to do a better job in their role of holding the executive to account.
So, let's review. The PBO is indeed a change to how our democracy works. But we have always evolved, so that's ok. Moreover, not only does the PBO not offend parliamentary responsibility of ministers, but by providing better information to parliament it actually enhances the notion of parliamentary responsibility that lies at the core of the Canadian system.