This morning Barbara Stewart's Electoral (Reduction in Number of Members of Parliament) Amendment Bill was drawn from the ballot. The bill would reduce the number of MPs to 100, by amending s191 of the Electoral Act 1993 to effectively reduce the number of list MPs (interestingly, s191 seems to be the only place the size of Parliament is defined). The number of electorate seats (or rather, the mechanism for allocating them) is left unchanged, as the relevant section (s35) is entrenched and requires a 75% majority or a referendum to amend. The change would take place at the next election
Like DPF, I oppose this bill, for the simple reason that it would break MMP. Overhangs would become much more likely, and they would generally be major-party overhangs rather than the minor party overhangs we have so far experienced. For example, in the 2002 election, Labour won 45 electorate seats and 41.26% of the party vote. Under Stewart's bill, they would have received no list seats, and held 2 more seats than they were entitled to (the difference being due to the "wasted vote", those parties which failed to make the 5% threshold). And this would become increasingly common, due to both the cube rule and the fact that the number of electorate seats will continue to grow at the expense of the list.
A second reason for opposing this bill is that it would undo all the progress that has been made in reducing the power of the executive. Since the shift to MMP we've seen a growth in the power of select committees, who now actually look at legislation rather than merely rubberstamping it, and even launch their own inquiries against the wishes of the government. This is essentially a function of the size of the House - there are enough backbenchers to pay proper attention to the job - and a smaller House would mean a lot less effort in this area. And that, IMHO, would make our democracy very much the poorer.