Opening up the Constitution for any reason, is a really dangerous thing to do. To start, Quebec isn't even a signatory to our current constitution, and a lot of provinces have grumbled about the special rights that are alloted to the people of Quebec. We may say we want to open it up to put in a requirement for referendum on tax increases, but then you need to be prepared for numerous rounds of constitution consultations and every province is going to want its say. Modifying the constitution requires the heads of province to approve it, at a very high ratio. It's not something that the federal parliament controls, and although there's a lot of stuff I wish was in there, it would be very difficult to get passed. So, no. I don't think opening the constitution would be particularly good for anyone, even if it would limit tax grabs.
That being said, there are many different ways to do taxes. Generally the most profitable is through "Value Added Taxes" (VATs), like the GST. That's a part of the reason why even though the Cons increased the income tax to "make up for" the decrease in GST, they actually brought in less money. That's a part of the reason why we're running a deficit again, as opposed to having a yearly surplus and actually paying down our debt as we were at the end of Liberal rule. Interestingly enough, the myth of the financially sound conservative is better applied to the Chretien Liberals than to Harper's Conservatives. Weird as that may seem.
Placing restrictions on the ability to raise or lower taxes won't work. Much as Concerned Citizen said:
The government SHOULD NOT spend more than it makes
Expanded, NO ONE SHOULD spend more than they make. How many people here have debt? Even the younger members of this board are probably thinking about college/university and know that debt is about to become a reality for them. Debt is created by spending more than you make, under the rational that some day, we will be able to pay it off. The reality is, with our current systems in place, the government, like the people of Canada, spend more than they make.
By putting in place a law stating that no government can create, alter, or remove taxes without a referendum, we're crippling the ability for things to happen. We would actually be crippling our own platform, namely the guarantee of broadband internet, and the net neutrality platforms. Both of these will in-turn require substantial government spending. The money has to come from somewhere. Cutting program spending, or moving it to different programs is difficult, and sometimes impossible for a government to accomplish. Ask any committee/department what they can cut to save money, and the list is tiny, if at all existent. It's all "essential". A shot in the arm of fresh tax money, like the "minor" increase caused by it becoming HST for Ontario and BC recently, can often give that wiggle room.
If we want to stand by our platform, we're going to have to start to cost our platform. And we'll have to come to terms with the fact that this cost, is in addition to the current budget that the PMO can't currently afford.