Speaking in Brussels on Wednesday, European Council President Donald Tusk said the "deal" he mediated between the European Union and the United Kingdom could not be reversed by the European Court of Justice. The EU's 28 member states had accepted "unanimously a legally binding and irreversible regulation for the United Kingdom in the EU," Tusk added.

He was reacting to an earlier comment by British Secretary of State for Justice Michael Gove. Gove said the UK's special status, which Prime Minister David Cameron had negotiated with other European leaders, could be changed by European courts if British citizens voted to remain in the EU.

EU membership and refugee crisis

Tusk said there was a danger of driving Britain out of the bloc if EU countries kept fighting about refugees. Handling the migration crisis would be of "key significance" to the June 23 referendum in Britain.

"All those who want to keep the unity of the European Union, the unity of the whole of the West … should back such a common plan with the fullest determination possible," said Tusk, a former Polish prime minister.

"If this emerging unity of action on the migration crisis is violated - by anyone - they may in fact contribute to the UK leaving the EU," he added.

The European Council president's comments came shortly after Hungarian Prime Minister Viktor Orban announced a referendum on EU plans to implement mandatory quotas for refugee distribution among member states.

Britain's exit, or "Brexit," would "change Europe for ever and it would be for the worse," Tusk said.

Meanwhile, five ministers from British Prime Minister David Cameron's cabinet, including Gove, have joined the ranks of Brexit supporters. However, 12 former senior officials in Britain's military wrote in the "Daily Telegraph" that Britain's security interests would be safest if the country remained in the bloc.

The EU has helped Britain in protecting itself from the "Islamic State," they wrote, adding, as a member of the EU, Britain would be "stronger" in a "dangerous world."

mg/sms (AFP, AP)