Leading article: A result that confirms our electoral system is broken

This most extraordinary of general elections has upset many expectations and preconceived opinions.

But the 2010 national vote has left untouched the central fact of British politics: the rottenness of our voting system. The ballots from 650 constituencies around the United Kingdom have almost all been counted. And one picture, at least, is clear: the main parties' share of seats in the new House of Commons does not reflect their share of the popular vote.

The Liberal Democrats are the primary victims of this broken system. Despite marginally increasing their share of the vote, they have ended up losing seats. Meanwhile, the Conservatives and Labour together won around 65 per cent of the popular vote, but take 86 per cent of the seats. Unfairness is hard-wired into this voting system.

And even the supposed practical advantages of first-past-the-post have failed to materialise. The traditional argument from defenders of the present voting system is that it can be relied upon to deliver clear mandates for single parties. Well, it certainly failed to do that on this occasion. This newspaper was sanguine about the prospect of a hung parliament, with no single party in overall control, in the run-up to this poll. We deplored the manner in which the Conservatives tried to use the prospect to scare voters into their camp. And we do not resile from that position now.

There remains no reason why our three largest parties should not be able to combine to allow government to continue to function. This is, after all, something most of our European peers manage to accomplish on a regular basis. But the argument that first-past-the-post is a fail-safe mechanism for "strong" government has been dealt a mortal blow. As the Liberal Democrat leader, Nick Clegg, argued yesterday, the moral and practical case for fundamental electoral reform is stronger than ever.

Of course, whether we are any closer to getting that reform or not is, regrettably, far less clear. All three of the main party leaders, not least Mr Clegg, have reason to feel bruised by the election result. The Liberal Democrat surge in the opinion polls did not translate into solid votes. There were excellent performances in parts of the country from the party, particularly where incumbent Liberal Democrat MPs were defending attacks from the Tories.

But the big two parties evidently managed to put a squeeze on the Liberal Democrats in scores of seats in the days immediately before the poll. There was not the breakthrough Mr Clegg and his party had hoped for. The electoral system is hopelessly biased against the Liberal Democrats and their evenly distributed national support. Yet even with this handicap, the party's leadership hoped and expected to do better.

The Labour Party's losses were by no means as catastrophic as looked possible at one point during the campaign, when the polls pointed to the party finishing third in the popular vote. But there was, nevertheless, a decisive swing against the governing party in large parts of the country. Many of the key gains from the New Labour revolution in 1997 were surrendered and the party's share of the vote sank to lows last seen in the mid-1980s.

But the party with perhaps the greatest reason to be disappointed by this result is the Conservatives. To grasp the scale of Mr Cameron's failure, it is necessary to take a step back and examine the larger context of this election. The Conservative leader was up against a widely unpopular government at the end of 13 years in office. The country had been through the gravest economic crisis since the Great Depression which left much of the electorate poorer or less economically secure. The national media was packed with influential and vociferous Conservative supporters. And the party's campaigns in marginal seats were lavishly funded by their billionaire deputy party chairman, Lord Ashcroft. They had wide popular approval at one stage too. In August 2008 the Tories enjoyed a lead of 20 per cent over Labour in the opinion polls. Yet despite all these advantages and a very professionally-run campaign, Mr Cameron still failed to win an outright majority of seats.

Some commentators have spoken about Mr Cameron's "momentum" coming out of this campaign. But, in fact, Mr Cameron's momentum has been slowing for the best part of two years. The Tory share of the popular vote ended up only 4 percentage points greater than that won by Michael Howard in 2005. It would be a big stretch to analyse this result and conclude that there exists popular enthusiasm for a Conservative government in the country.

The rather traumatic experience of all three parties in the polls this week is influencing the post-election haggling. Mr Brown, Mr Clegg and Mr Cameron all delivered sober addresses yesterday upon their return to London. And all three leaders appeared chastened. They each seemed to acknowledge that they and their parties have been treated without much enthusiasm by the British public.

But, as for much of the campaign, it is Mr Clegg who finds himself in the spotlight. Both Labour and the Conservatives are seeking to do a deal with the Liberal Democrats, which will allow them to govern. Mr Clegg now has a difficult choice to make. Mr Brown is offering the Liberal Democrats an immediate referendum on electoral reform, the party's long-standing and primary objective. David Cameron, by contrast, is suggesting only an "all-party committee" to look at the case for change of the electoral voting system.

The Labour offer is far superior. Mr Cameron's proposal for yet another committee on the subject sounds like an attempt to kick the issue into the long grass. The case for electoral reform is already made, not least by the comprehensive 1998 report by the Jenkins Commission, which recommended an elegant Alternative Vote Plus voting system. AV plus would combine the merits of greater proportionality with the traditional constituency link.

Yet, depressingly, it is hard to see Mr Clegg going into partnership with Labour. The two parties combined would still not have enough seats to form a majority in the Commons. They would need to rely on votes from Scottish Nationalists and Northern Ireland unionists. A Labour-Liberal Democrat coalition would be inherently more unstable than a Conservative-Liberal Democrat accommodation. And Mr Clegg, with the wind sucked from his sails by the Liberal Democrats' disappointing performance in the vote, is going to find it much harder to summon the courage to side with the weaker of the two larger parties.

Yet Mr Clegg should not roll over on the principle of electoral reform. There was a lot of talk of the national interest yesterday. A fair voting system is firmly in that interest. Mr Clegg and the Liberal Democrats should use what leverage they have to fight for it, and fight hard.