BBC News - The realities of re-negotiating Europe At some point in the future - and particularly if David Cameron wins the election in 2015- the UK will attempt to re-negotiate the terms of its membership of the EU. It will be a long, tortuous process, strewn with potential difficulties. In most areas, although not all, returning powers to Westminster will require a change to EU treaties. The British Government is convinced that fixing the eurozone crisis will need treaties to be altered. Officials in London and Brussels believe that closer EU integration is necessary for the eurozone's survival and that will require a new legal underpinning. The European Commission has said it will come up with proposals for treaty change by next May, The German government, too, believes that banking union will require a change to the treaties at some stage. That will open the door for the UK to raise its own demands. Treaty change would trigger an inter-governmental conference and any country can bring its own list of proposals. Treaty change requires unanimity and that is both a strength and a weakness for the UK. Unforgivable sin If the UK did not get concessions it could potentially block the treaty change but, if that was regarded as essential to helping the eurozone, it would make Britain extremely unpopular. As far as Berlin is concerned that would be the unforgivable sin. At his lengthy news conference on Thursday, French President Francois Hollande said: "I can understand countries don't want to join the euro, but they cannot impede the consolidation and strengthening of the eurozone and if they want to go further and refuse powers, then the risk is of a splintered Europe." In any event, some countries are opposed to any moves which would make the UK a special case. It will be tough to get all 28 countries to agree to Britain winning back some powers. Also, any significant change to the Lisbon Treaty - the constitutional basis of the EU - would almost certainly trigger referendums. France, in particular, wants to avoid this. The government in Paris is wary of consulting French voters at a time when the mood is increasingly sceptical of Europe. President Hollande has not forgotten that the French people rejected an EU constitution in a referendum. So the French would only want an adjustment to the existing treaties. In one area - justice and home affairs - the UK already has an opt-out, set out in the Lisbon Treaty. It means Britain can stand aside from the European arrest warrant for example. Arousing suspicions The German government, which remains keen to keep Britain in the EU, shares the view that some powers could be returned but German ministers are saying any changes would have to apply to all countries with no further opt-outs for Britain. Another option for Britain would be to try to have some legislation repealed - like the Working Time Directive - which sets out the number of hours which can be worked. It might be possible to negotiate a concession here but then the question is whether it would be regarded as significant enough to qualify as a fundamental change to Britain's relationship with the EU. The government would almost certainly want concessions on social and employment legislation. The problem with this approach is that some countries would fear and suspect that Britain was negotiating for itself a competitive advantage. The government has not yet said what its demands would be. It is still assessing what "competences" should stay with Brussels or should be returned. The original plan was not to begin any re-negotiation until it was clear what the "new" Europe would look like and where that left the UK. It may still take years for Europe's new architecture to emerge and that might further complicate the government's task. It is safe to say that nothing will happen swiftly.