The president of the European Parliament, Martin Schulz, has warned David Cameron that his attempt to negotiate a new relationship with the Europe could lead to the break-up of the EU.
Writing on The Huffington Post UK on Thursday, the German MEP warns the prime minister that any attempt by the UK government to repatriate powers to Westminster is likely to be a "drawn out and cumbersome negotiation".
"By attempting to revisit major parts of the Union's established acquis and picking and choosing the bits the UK approves of is a dangerous precedent - it could lead to piece-meal legislation, disintegration and potentially the break-up of the EU," he says.
Schulz said the UK had played a major role in shaping EU policies and it would be unfair for it to then try and wriggle out of obeying many of them.
"Surely it cannot be expected that the EU institutions and the other 26 Member States will stand idly by whilst the UK moves increasingly closer to opting out of more than 130 of those measures - in essence re-erecting national borders in the fight against cross-border crime - and then seek special agreement to rejoin a select few which are considered to be in the 'national interest'.
Schulz's intervention comes a day before the prime minister is due to deliver a major speech in Amsterdam on Britain's future membership of the EU.
Cameron is expected to set out plans to persuade the UK's EU partners to allow London to wrest back control over several areas of policy with a view to putting the new deal to a referendum after the next election.
Schulz adds: "In a globalised world, it is not in the UK's interest to seek to downgrade to some kind of 'second class' membership and so choose to weaken its own influence on European and global affairs.
"Attempting to repatriate competences from the EU may well play well in parts of the notoriously eurosceptic media and in parts of the Conservative Party but I would question whether it is truly in the British and European long-term interest."
"I suspect however that David Cameron is playing a dangerous game for purely tactical, domestic reasons.
"I personally do believe him when he says that he wants the UK to remain a Member of the EU. But he increasingly resembles Goethe's poem The Sorcerer's Apprentice who cannot get rid of the spirits that he summoned - the spirits who want to leave the EU for ideological reasons to the detriment of the British people."
Senior Lib Dems including Nick Clegg and Vince Cable have joined Ed Miliband in warning any pledge to hold a referendum would create "uncertainty" and damage the British economy.