At this morning's Labour Party press conference, I asked Lord Mandelson, the party's election campaign chief, how Labour can claim to advocate root-and-branch political and constitutional reform when it is offering a referendum on changing the electoral system from first-past-the-post (FPTP) to the Alternative Vote (AV).
Under the Alternative Vote the Liberal Democrats would fare much better. Under this system voters place candidates in rank order - 1, 2, 3 and so on. If no candidate wins 50 per cent of the first-preference vote, then the votes of candidates at the bottom of the poll are redistributed in accordance with those voters' second preferences, and so on, until someone passes the 50 per cent mark.
Nick Clegg's party tends to be everyone's second choice. As many as 68 per cent of Labour supporters say they would give a second-preference vote to the Liberal Democrats, as do 41 per cent of Conservatives.
So if the Liberal Democrats are running second in a constituency, they can hope to leapfrog into first place on the back of second preferences cast by third-placed Conservative or Labour supporters.
The party might win up to twice as many seats -- 217 -- as they would under the current system.
Yet it would be Labour, with 238 seats, that would still be the largest party. The Conservatives, meanwhile, would be a poor third with just 163 seats.
. . . So, under Labour's proposed alternative, not only would the party that was third in votes still come first in seats, but in addition the party that came first in votes would be a poor third in seats. One wonders whether voters will regard this as an improvement.
Indeed. And Curtice is not alone in his analysis of AV and its flaws -- Roy Jenkins's report on electoral reform, commissioned by Tony Blair and published in 1998, concluded that the Alternative Vote would have delivered an even bigger majority to Labour in 1997.
This morning, however, Mandelson chose to fob me off with a line about Labour being the only party offering a referendum on electoral reform. True. But what kind of reform? Is AV fair enough? Does it go far enough? And, perhaps above all else, will it be enough to buy Lib Dem support in a hung parliament? I very much doubt it.