Demands for electoral reform are invariably about political advantage. So Alan Johnson’s endorsement of the plan produced by the late Lord Jenkins of Hillhead in October 1998 invokes comparison with the reaction to the death of Metternich, the wily Austrian statesman of the 19th century — “Now what did he mean by that?”

First and foremost, Mr Johnson wants to present himself as a political reformer at a time of turmoil regarding MPs: in his own words, overhauling the engine, not just cleaning the upholstery. But his means of doing so are bold and unexpected.

The Jenkins report seemed to have been long forgotten. The commission was set up after Labour’s 1997 victory to honour a joint agreement on constitutional reform with the Lib Dems. The recommendations balanced several factors: the preservation of the constituency link; giving more voters a say in the outcome; and retaining the possibility of single-party government when the winner was well ahead (as in 1983, 1987, 1997 and 2001, but not 1992 or 2005).

The Jenkins plan involved a hybrid system called AV plus. About four fifths of MPs would be elected, as now, for single-member constituencies but on the basis of the alternative vote. AV involves listing candidates in order one, two, three so a winner has to secure a half of the preferences plus one. This is unlike the first-past-the-post system, where a winner just has to be ahead of the runner-up.

Jenkins argued that AV on its own was unacceptable “because in anything like present circumstances it might increase rather than reduce disproportionality” (between votes cast and seats won). Consequently, he urged a top-up of between 100 and 120 MPs elected through a second vote from counties and metropolitan districts to reduce this imbalance. This would ensure that where, say, Labour had won all the seats in an area, the top-up would go to the Tories and Liberal Democrats.

The report was immediately rejected by Jack Straw, then, as now, in charge of constitutional reform. He reflected the hostility of a majority of the Cabinet and Labour MPs, and Tony Blair did not feel committed enough to back the report. Nothing has happened since then. However, all the devolved bodies — in Scotland, Wales, Northern Ireland and London (as well as the European Parliament) — have been set up using a form of proportional representation.

Since then, and especially as Labour’s standing has declined, there has been a revival of interest in AV in the Cabinet and among left-wing think-tanks: even Mr Straw has expressed interest in re-examining the issue. The Conservatives remain strongly opposed to any proportional system.

Mr Johnson’s proposal that a referendum be held on the choice between AV plus and first-past-the-post on the same day as the next general election is intended to portray Labour as reformers even though there would be no government recommendation. If the outcome of the general election were a hung Parliament, but voters backed AV plus, there would be a strong incentive for the Lib Dems to support Labour, since the Tories would oppose the change. So what Mr Johnson is really talking about is an attempted Labour rescue plan or lifeboat in the face of the storm of public disillusionment.

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