Should there be a referendum on PR?

The Conservatives are vowing to filibuster attempts by the governing Liberals to reform the way we elect our MPs - be it alternative vote or some kind of proportional representation, unless there is a referendum. Normally, changing the rules for representation only requires a vote of Parliament. But this just might require a constitutional amendment of the kind that requires the consent of at least seven provinces, especially if we're going to tinker with the idea of proportionality for the provinces.

Remember that several provinces are over represented thanks to a grandfather clause - if there were strict proportionality, Saskatchewan would have 10 members, Manitoba 12, New Brunswick 7, Prince Edward Island 2, Nova Scotia 9, Newfoundland-Labrador 5. Instead, they have 14, 14, 10, 4, 11 and 7, respectively. Will a new PR system require provinces get strictly what they're entitled to and no more?

Also, there is the issue of "overhang" seats. This commonly happens in Germany, when a party's percentage of the popular vote means it gets fewer seats than the number of constituencies they're entitled to by that vote - or vice versa. In such case, new seats are created out of fresh air and people on party lists who might not have been entitled to be elected, end up with seats.

What could that mean? Presume we stick with 338 seats, but after the votes are counted about 20 overhangs are created. Where to sit them?

You may have noticed a change in seating arrangements for this Parliament. The seats used to be two by two. To make room for the 30 new members this year, the seats had to be arranged so members now sit in blocks of five.

One could argue if we're going to have a referendum on this, then the entire constitution will have to be reopened. I don't think so. But I think there's a point here. In every country I'm aware of that has made the switch from FPTP to something else, voters were asked first. So, I think we should be here, too.

For myself ... If it's alternative vote, I'd go against. But if we went to something like STV or MMR ... that is something I could support. I'd prefer the latter because you could vote for a list (i.e. for PM) for one party and a local candidate from another.