In theory this is the very worst time for politicians to be grappling with weighty and complex matters such as constitutional and electoral reform. We know that there will be a general election by next June at the very latest. And that tight timetable will be a powerful influence on thinking across Westminster.

Turkeys do not generally look forward to Christmas and many MPs will be wary of supporting reforms that could jeopardise their own chances of re-election. And those party leaders expecting the present system to deliver them some share of power also have an incentive not to rock the boat. In normal times, an atmosphere of intensified partisan self-interest and pre-election conservatism would smother any serious reform initiative.

Yet these are not normal times. And unlikely though it might seem, the hare of reform is now up and running. Gordon Brown held the first meeting yesterday of a Cabinet subcommittee with the rather grand title of "National Democratic Renewal Council" and will make a statement in the House of Commons on the subject today.

But the impetus for reform stretches across the parties. The Conservative leader, David Cameron, delivered a speech last month in which he spoke of the need for a "massive sweeping, radical redistribution of power". And the Liberal Democrat leader, Nick Clegg, has been demanding radical reform too.

We have, of course, the expenses scandal to thank for the sudden salience of this agenda. The Liberal Democrats, to be fair, have always advocated reform, but it is unlikely that Mr Brown and Mr Cameron would be making statements on the need to redistribute power were it not for the toxic revelations in the past month of MPs submitting claims for massage chairs and gardening bills.

Some common ground on reform, such as greater autonomy for Commons committees and allowing those outside Parliament to initiate debates, has already been identified between the parties. Such reforms would be welcome. And there is no reason why most of them cannot be enacted in the present Parliament, by amending the Constitutional Renewal Bill at present making its way through the House. The sooner such changes can be enacted, the better. Bigger changes, such as reform of the House of Lords and modification of the voting system, probably cannot take place this side of a general election. But that does not mean they should be kicked into the long grass. Parties should be actively developing reform proposals for their respective manifestos.

The voting reform the Government seems most likely to favour is the Alternative Vote (AV). In one sense this would be a disappointment. AV is scarcely more proportional than first-past-the-post. But it would be "fairer", requiring each MP to win the backing of at least half of their constituency electorate. And it could be a step towards the far superior "AV plus" system recommended by the 1998 Jenkins Commission. Moreover, it would mean a breaking of the taboo on meddling with the present unreconstructed and distorting parliamantary voting system.

Constitutional reform in Britain has always been a process, rather than an event. Now is not the time for those who want change to make the best the enemy of the good, but to bring pressure on our politicians to ensure this opportunity is not allowed to go to waste.