Andrew Grice: Cameron's self-serving electoral reform plans

Shock news: David Cameron is committed to electoral reform. His "reform" is to cut the number of MPs by 10 per cent and introduce fairness into the system by equalising the number of voters in the 650 constituencies.

The Tory leader supports the first-past-the-post system, saying it allows the public to kick out a discredited government and to choose their prime minister, while proportional representation (PR) leaves the choice of policies and premier to a stitch-up by politicians in smoke-free rooms.

On closer inspection, the Tory "reform" is little more than an attempt to play pendulum politics by reversing the bias in favour of Labour. In 2005, Labour won 55 per cent of the seats with 35 per cent of the votes cast. The Tories won 32 per cent of the votes and only 30 per cent of the seats, while the Liberal Democrats 22 per cent of the votes and only 10 per cent of the seats.

Mr Cameron's first Queen's Speech would include a Bill to ensure a high-speed review of the parliamentary boundaries. These wheels usually turn slowly, taking up to seven years. The Tories want it to happen within 18 months, so they can implement the new boundaries for the next election.

At present, there are wide variations in the number of people in each seat: the Isle of Wight has 107,000 voters, well above the proposed new target of about 77,000.

To Labour, the Cameron plan is nothing less than "gerrymandering", the Tories' revenge for being outsmarted in the ground war of local hearings in previous boundary reviews. On the current electoral map, Labour's vote is much more "efficient" in translating votes to seats than the mountain of votes piled up by the Tories in their heartlands. Under first-past-the-post, this raises the bizarre prospect of Labour coming third in the overall share of the vote and winning the most seats – as several polls during this campaign have suggested.

Labour is hardly whiter than white. It does now favour real rather than bogus electoral reform – the Australian-style alternative vote (AV) system in which people rank candidates in order of preference. But it is not PR.

Sadly, today's election will be conducted under a system which gives huge weight to about 100,000 swing voters in the 100 key marginals. They will decide it.