London could make EU 'unravel'

"If every member state were able to cherry-pick those parts of existing policies that they most like, and opt out of those that they least like, the union in general, and the single market in particular, would soon unravel."

"All member states can, and do, have particular requests and needs that are always taken into consideration as part of our deliberations. I do not expect any member state to seek to undermine the fundamentals of our co-operative system in Europe."

Van Rompuy's comments come as British Prime Minister David Cameron has been increasingly struggling to contain his broadly eurosceptic Conservative party.

The struggle has become tougher since the onset of the financial crisis which has prompted other member states to seek further EU integration. Cameron's Conservatives see this as a threat to London's interests but also as an opportunity to loosen Britain's EU ties should the Union's treaties be re-negotiated.

Britain is already not part of key EU policy areas. It is not a member of the euro, it opts out of border-free schengen zone and, most recently, out of the single European banking supervisor.

Significantly, Cameron's government has also said it plans to opt out of swathes of laws in EU police and judicial cooperation. This has prompted exasperation in Brussels and other EU capitals - but also a keen sense of concern.

Britain is liked for its free market principles. Germany, in particular, is worried that British absence from the EU negotiating table would tip the balance in favour of more protectionist states, such as France.

EU officials have been pointing out that a British exit - already dubbed Brexit - would leave it with no global role and that other models for relations with the EU - such as Norway's trade-only deal with Brussels - would not suit it.

A British departure from the EU would be like seeing a "friend walking off into the desert," said Van Rompuy pointing to London's role in building the single market, and its expertise in foreign policy, finance and trade.

He also noted that the treaty change that Cameron is hoping to use as a springboard for getting EU powers back to London may never come to pass.

"The treaties allow a considerable degree of flexibility and much can be done without needing to amend them."

The next chapter in Britain's tempestuous relations with the EU is set to be opened early in the new year when Cameron is to give a highly anticipated speech on the European Union.

Smaller commission

Meanwhile the future-of-Europe debate is taking place in other member states too.

According to a report in the Sueddeutsche Zeitung, Germany's conservative CSU party - the Bavarian sister party of the ruling CDU party - is calling for a smaller European Commission.

In the future it should only have 14 European Commissioners instead of the current 27 says a draft party paper due to be agreed in January.