Leading article: The growing pains of the Liberal Democrats

Mr Clegg must prove his MPs are not simply lobby-fodder for their Tory Coalition partners

With the Liberal Democrats in Gateshead for their spring conference this weekend, NHS reform is once again top of the agenda. And once again grassroots activists are threatening rebellion. It would be a mistake – for the NHS and also for the party. It is time to make peace and move on.

Last year's conference was a seminal moment for the Health and Social Care Bill. Outspoken Liberal Democrat opposition, led by Baroness Williams, forced the Government to rethink key parts of the package. Despite another 140-odd modifications since, however, swathes of the party are still unhappy. Even Nick Clegg's carefully choreographed recent amendments – introduced with the backing of Lady Williams, no less – have not proved conclusive. And although a final decision will not be made until tonight, in all likelihood delegates will debate at least one of two emergency motions on the subject tomorrow morning.

It is a testing moment for the Liberal Democrats. For all the upbeat talk from Mr Clegg – with his call for the party to "tear off that rear-view mirror" and "get on with the job" – he has real concerns that party members could vote to veto the legislation altogether, and real problems if they do. Yesterday's tribunal ruling that the Government must publish their officials' gloves-off risk assessment of the reforms will only be grist to the mill of its opponents. Even so, it would be reckless for the Liberal Democrats to withdraw their support now.

It is true that there is much to be criticised. Bundling so much into a single behemoth of a Bill just as health service budgets face a £20bn squeeze was grossly ill-judged. But the central tenets – to cut bureaucracy and boost competition – remain the right ones and should be pursued.

The Liberal Democrats would also pay a high political price for a volte-face. After months spent amending the Bill, to vote it down now, with barely more than a week to go, would smack of political immaturity, if not outright disingenuousness. Better to claim credit for improving the original plans and let the legislation pass.

That said, the contretemps makes it more important than ever to set out a convincingly Liberal Democrat agenda. The NHS reforms may not have sparked quite the same outrage as the undeniable U-turn over tuition fees, but they have proved dangerously divisive among the party's traditional supporters. Mr Clegg's primary task now must be to heal the breach, proving both to voters and activists alike that he and his colleagues in Westminster are more than just lobby-fodder for their Conservative Coalition partners.

Arguably, the NHS reforms are a case in point. Without the brouhaha from the Liberal Democrats, the Bill would have been passed, unamended, a year ago. But, despite the best efforts of the likes of party president Tim Farron, the message has been lost in the noise.

As the Budget approaches, the Liberal Democrats have another, more tangible, opportunity to make their presence count: tax. With the Chancellor casting around for ways to boost growth, what better than to trade an agreement to abolish the 50p top rate for expedited plans to raise the income tax threshold? And, to pay for the scheme, there are two other Liberal Democrat favourites – a mansion tax and reduced top-rate pension relief.

It is never easy to prove the counter-intuitive, to demonstrate with certainty that a situation would otherwise be worse. That was always going to be the challenge for the Liberal Democrats in coalition. Tax is an opportunity to prove their progressive worth. Voting down the NHS reforms is not.