Gordon Brown is not famed for his public speaking, but in the past week Westminster has hung on his every word. Speculation of an October election has been rife. But this is beginning to look like a treacherous option for the new Prime Minister, with The Times poll this week suggesting that a hung Parliament is now a real possibility. Wheeling and dealing in the murky world of coalition is not a prospect Mr Brown will welcome.

And he’s right to fear it. Consensual politics is one thing; pacts and deals quite another. Coalitions are difficult, uncertain and potentially deeply destabilising for both the country and the parties involved. That is why it is wrong to call for Sir Ming Campbell’s departure. His intellect, experience and calm approach is just what the Liberal Democrats will need to navigate the tricky waters of a hung parliament.

But Ming needs to come out now and state that, in the event of a hung Parliament, the Liberal Democrats will work with whichever party has the most MPs. For the Lib Dems, completing the Blair/Ashdown project or trying to establish a new progressive agenda with Labour may have strong emotional and practical appeal. But it would have been unthinkable for the Liberals to have entered into a partnership with Mr Blair’s Labour Party, which oversaw such extensive Whitehall centralisation, offended civil liberties with its terrorism legislation and ID cards, and invaded Iraq. It remains to be seen if Mr Brown will genuinely take his party in a direction more acceptable to the Liberals.

Times have moved on. That means opening up the possibility of talking to David Cameron’s Conservatives. Many people may be surprised by how much shared agenda there is between the two parties. On the environment, civil liberties and localism the two parties share some common ground. 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.

However, Ming’s relations with Mr Cameron are not as close as with Mr Brown: he has made more personal attacks on Mr Cameron and gone out of his way to dismiss talk of a deal with the Conservatives. This should not be a given. Ming must not allow his close relationship with his Fife neighbour and airport lounge companion to cloud his judgment about which of the two main parties we can work most effectively with to defend and prosecute a liberal agenda.

As the election draws closer, and as Mr Brown distances himself from the Blair years, we may see more Lib-Lab talks – but we must not assume that the forces of liberalism should necessarily exclude the Conservatives.

Mark Oaten is Liberal Democrat MP for Winchester. His book Coalition is published next week

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