Leading article: The European political battlefield

The demotion of Baroness Kinnock to the Foreign Office Africa portfolio after only four months as Europe minister may look unjust – after all, Parliament was in recess most of that time and the new minister had scant opportunity to show her mettle. What is more, the appointment of Chris Bryant to replace her, with a lower salary, a lesser status and without a seat at the Cabinet table, suggests a downgrading of the post.

Yet the thinking behind the Prime Minister's decision to move the Europe minister post back to the Commons is quite right. Now that the Irish have voted "yes" in their second referendum, the Poles have ratified the Lisbon Treaty, and the Czech President – the last hold-out against the treaty – is coming under increasing pressure to reach a deal with Brussels, the Europe question is inexorably returning to the British political agenda. In the run-up to the general election, the Government has to be able to take the fight on Europe to the Opposition as though it means it. To have the Europe minister in the Lords, rather than speaking directly up against his or her opposite number in the Commons, would make any debate limited and restricted in its resonance.

So far, Mr Brown has seemed reluctant to debate Europe with David Cameron, while the Foreign Secretary has concentrated on the narrow issue of the Conservatives' dubious Continental friends, following Mr Cameron's decision to withdraw his MEPs from the mainstream centre-right alliance in the European Parliament. That decision looks increasingly ill-judged. But the weakness in the Conservatives' position stems from more than their questionable alliances in Brussels. Assuming the Lisbon Treaty comes into force before the British election, which looks more and more likely, this solves one problem for Mr Cameron, in that it will free him from his commitment to hold a referendum. What it will not do, however, is heal the deep divisions in his party over Europe.

This is a vulnerability that Labour and the Liberal Democrats have a perfect right to exploit as the election campaign approaches. They should make the most of it, arguing the case for Britain's wholehearted participation in the European Union at every opportunity.