The coalition question. Again.

Mark Oaten won't have made himself very popular today. In a very disjointed article in the Times, he argues that a hung parliament now looks likely; that if it happens, the Liberal Democrats should agree to enter a coalition with whichever party is the larger; that we should therefore be prepared to ally with the Conservative Party if necessary; and that the Tories aren't really so different from us anyway.

Nothing derails the Lib Dems more effectively than speculation about a hung parliament. We need a well thought-out, reasonable, and above all, consistent answer. The fact that the question keeps coming up, again and again, shows how badly we usually tackle it. And of all the dreadful attempts, this one by Oaten has to be the worst I've ever seen.

The premise behind the article is shaky to start with - we are not staring a hung parliament in the face. Even taking the figures from the Times' poll on Tuesday, Brown would still have a majority. The last hung parliament was fully a third of a century ago; the one before that was in the year my granny was born. Under Britain's rather eccentric voting system, they come along very rarely, and when they do come, they don't last long. We need to let people know that the idea of a hung parliament isn't credible, and that it only gets so much airtime because the other parties know it gives us a headache.

But just suppose Oaten's right. Brown calls a general election, the vote splits three ways, and any possible combination of Labour, Tory and Lib Dem could form a government. Would we really be right to insist on dealing only with the larger of the other two parties?

The largest party in Parliament clearly deserves to have the first go. However, any grouping with a majority of the seats can legitimately form a government. Talking to either party would be morally acceptable. The guiding factor should be political principles, not numbers. That doesn't mean it would be unthinkable to ally with the Tories - but if we did, it would be because we managed to reach a genuine agreement, rather than because they had a half a dozen MPs more than Labour.

Mark Oaten believes we have plenty of common ground with the Tories. He arrives at this conclusion because "recent votes have seen the Lib Dems walk through the House of Commons lobby with the Tories more often than with Labour in protecting liberal values." Perhaps. But then again, perhaps it's because we're both parties of opposition, in a system where politicians can have a nuanced debate in the chamber, but are forced to make a polar choice in the lobbies.

I know I keep banging on about the importance of the Lib Dems being independent, but it's so crucial, it just can't be overstated. If we give the slightest hint that we're endorsing the Tories over the Labour, we give both of them an open invitation to squeeze us like a floppy yellow sponge. Cameron can say "why vote Lib Dem, when you can vote for the real thing?" Brown can say "if you dislike Cameron (and who doesn't?), Labour are the only choice." Exactly the same process will happen in reverse if we appear to be endorsing Labour.

The only way to get rid of the coalition question is to refuse, point blank, to give any preference to either party. Instead, we have to pledge to sit down with both of them, in the event of a hung parliament, and try our best to agree on a Queen's Speech that would be true to our liberal principles. We have to promise not to enter government, with either party, unless we can agree on a programme of legislation that doesn't betray our manifesto, and where every compromise we make, for the greater good, is explained honestly and openly to the public. That would be the most responsible way to navigate a hung parliament, should it ever occur, and far more effective than some pre-determined strategy based on crude numbers (Oaten) or personal chemistry (Ashdown and Campbell).

Perhaps the best way to turn this back on Labour and the Tories is to point how close together they now are, and argue that they'd do best to form a German-style grand coalition with each other. It's a very cheeky answer. But it's no cheekier than our opponents branding us as opportunistic, for hypothetically making the wrong choice in a non-existent situation.