It is fashionable in some pro-European circles in Britain to attribute the recent rise of popularity of the EU in opinion polls in Britain to the fact that two tricky issues seem to have been removed from the agenda: accession to the euro, and the Constitutional Treaty.

It was indeed an uphill struggle, at times, to argue the case on these important but complex matters. But pro-Europeans should not for one moment think that these issues have disappeared forever.

We can certainly stay out of the euro in the short-term but in the long-run staying out means losing out. And now that the euro appears to have overcome some teething problems, the terms of this debate may well alter over the coming years.

Similarly, for the Constitutional Treaty. It may have been kicked into the long grass following the French and Dutch referendums, but the 'period of reflection' comes to an end next June when the European Council summit is due to examine a way forward on this issue. Meanwhile, various countries have continued the ratification process and by next June eighteen are likely to have done so. They will want to keep the constitution intact, or as intact as possible. But even if that is not possible, the issues that the Constitutional Treaty was intended to resolve have not disappeared and Member States will have to return to the questions of how to make the EU function more effectively as it approaches 30 Member States, how to improve its democratic accountability and how to make it easier to understand for citizens.

In theory there remains a wide range of possible options, and it is certainly premature now to decide which one of them might be politically feasible next year or later. But two main variants are emerging in the debate. One is re-negotiating the draft constitutional treaty (simply adding protocols to it seems to be an option that is fading). This would take some time and the negotiations would be protracted and complex.

The alternative is to adopt quickly a 'mini-treaty' focusing on the less controversial institutional changes that are necessary to pursue the further enlargement of the European Union. These would be modest and would not rise above the threshold that would trigger referenda in certain countries. In other words, they would give no new responsibilities or competencies to the European Union, whose remit would remain unchanged, but would streamline the institutions (notably a smaller Commission), reform voting procedures and the rotating presidency in the Council and improve democratic accountability.

Interestingly, the items contained in this second option are all issues that would, in any case, have to be addressed in the context of the next accession treaty - presumably with Croatia. The current treaties (as last amended by the Treaty of Nice) contain no provisions for new member states beyond Romania and Bulgaria. If the issues haven't been solved before that, the Croatian accession treaty will anyway have to settle how Croatia will be represented in the institutions. This means that the voting system in the Council will have to be reviewed, (with many countries advocating the system all governments agreed to in the constitutional treaty), reviewing the size of the Commission (which has to be reviewed anyway in 2009 under the current treaties) and the rotation system for the Presidency of the Council and the European Council.

Of course, ratifying an accession treaty will be less controversial than a general Constitutional Treaty, even if the later was no more than a collection of about a dozen useful reforms. There is no reason why an accession treaty should not contain 'emergency repairs' to the EU system, while leaving more fundamental reform to a more long-term process.