José Manuel Barroso, the President of the European Commission, picked the wrong party conference to address. He was preaching to the converted in Brighton yesterday, and duly received a standing ovation for a balanced restatement of the pro-European case. But his speech is far more needed elsewhere, either at the Tories, if they are prepared to give a fair wind to a positive message from Brussels, or at Labour, with its doubts and hesitations over making a pro-EU case.

At present the sceptics are making the running. They have captured the propaganda high ground with their call for Gordon Brown to honour his predecessor’s promise of a referendum because the reform treaty is largely the same as the old constitution. The Government’s response that the two are conceptually different sounds pedantic and legalistic. A stronger point is that the Government’s red lines and opt outs, negotiated by Tony Blair in June, mean that the treaty applying to Britain is the not the same as that affecting the rest of the EU.

This compare-and-contrast exercise is secondary, however, to the basic question of the substance of the treaty. Admittedly, there are questions about the legal sustainability of provisions limiting the applicability of the charter of fundamental rights to Britain but, as a whole, the treaty is not nearly as important as, say, the Single European Act or the Maastricht treaty. Many of the institutional changes make sense in an enlarged EU of 27 member states.

Underlying these arguments is the basic question of the pros and cons of Britain’s membership of the EU. British pro-Europeans too seldom make that case. As Nick Clegg argued yesterday: “How are we supposed to deal with the environment, cross-border crime, world trade or global migration other than by way of supranational arrangements at EU level?” Focusing on transfers of power, always described as surrenders, ignores the advantages of pooling sovereignty. Mr Clegg epitomises a younger generation of Lib Dem Euro-realists, rather than an older group of Euro-enthusiasts mistrustful of nation states and keen on all things EU, such as Andrew Duff, the leader of the party’s MEPs.

Mr Barroso argued reasonably that in a globalised world it was necessary for action on a EU-wide level, notably on climate change. We cannot isolate ourselves from pollution from elswhere. Chris Huhne rightly argued in his speech about a carbon-neutral Britain that national initiatives must be completed by EU action. Lib Dems and Labour ministers such as David Miliband agreee on the environmental union aspect of the EU.

Yet as Mr Barroso said, if you want economic reforms, you must have the means to deliver them, more effective EU-wide institutions and enforceable rules. Hence, the reform treaty.

The Lib Dem leadership remains unsure how to play Europe. Sir Menzies Campbell is under pressure from some MPs, notably in the South West, worried about the tide of scepticism. Hence, he has sought to trump calls for a referendum on the treaty by proposing an in-out ballot on British membership of the EU. This has annoyed some of his younger allies, who fear that it will play into the hands of opponents of the reform treaty. He should concentrate instead, as he did yesterday, on making the case for what Britain gains from playing an active role in the EU.

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