Britain faces opposition from European partners over plans to reform the EU ahead of an in/out referendum on membership, and should not expect “Europe a la carte,” the European Parliament president warned Friday.

Martin Schulz welcomed Britain’s push to make the European Union more competitive, but said other demands would “set a dangerous precedent for a Europe a la carte”, where countries could ignore aspects of the EU they did not like.

The reforms would “meet resistance in the European Parliament”, Schultz told students at the London School of Economics (LSE).

The German politician also criticised Cameron’s call for recognition that the EU had more than one currency.

“The currency of the union is the euro, the treaties are very clear on this and the treaties also guarantee an opt-out for the United Kingdom,” he said.

“Giving a de facto veto to any member state of the European Council on eurozone issues is unacceptable” and risks “paralysis for the eurozone,” added Schulz.

He revealed that Cameron had told him it was not Britain’s “goal” to hamper the eurozone during a meeting earlier Friday.

Schultz conceded that Britain had genuine concerns over its controversial demand to reduce welfare to EU migrants.

“If movement creates practical problems, if there is systematic abuses, if schools are overcrowded and hospitals overstretched as the British government states, of course these problems have to be solved,” he said.

“But a solution cannot come at the price of discriminating against EU citizens,” he stressed.

Cameron has promised a referendum on EU membership by the end of 2017, but it could take place as early as June.

The possibility of a “Brexit” is the latest crisis to hit the EU, and Schulz urged voters to remain in the union.

“We Europeans have to stick together more than ever,” he said.

“Many of my colleagues say behind closed doors: ‘Don’t stop a rolling stone. If the Brits want to leave, let them leave’.

“But Europe needs the UK with its foreign policy experience and clout, its open market policies and its trade track record,” Schultz said.