It could take up to seven years to renegotiate relations between the European Union and the UK if Britain chooses to leave the bloc in the 23 June referendum, warns the chief of the European Council, Donald Tusk. While the terms of the agreement can be drafted sooner, he warned the implementation process could consume as many as seven years, during which time UK's relations will essentially be in limbo.

Even as the war over whether the UK's ties with the EU should be severed heats up within the country, Tusk, who is the head of one of EU's key bodies, spoke to Berlin-based daily Bild warning against a "Brexit".

"Every single one of the 27 member states as well as the European parliament would have to approve the overall result. That would take at least five years, and I'm afraid, without any guarantee of success," he said adding that the existing contractual ties could be dissolved in two years. The full version of the interview will be published on 13 June.

Tusk's grim warning has come just as the Vote Leave campaign has claimed that a deal with the EU would be quickly closed if Britain chooses to leave the union. The Leave side has also suggested Britain would be able to swiftly strike trade deals with non-EU states in order to make up for the Brexit vote.

"Every family knows: Divorce is traumatic for all," Tusk said, adding that economically, Brexit would be disadvantageous for everyone in the EU but mostly for Britain. He also warned: "On the day of withdrawal of the British, our external enemies would drink champagne. We should make every effort to destroy them".

However, Prime Minister David Cameron has repeatedly warned the UK leaving the EU would throw a decade-long uncertainty. Most of the EU leaders have also rallied against Britain exiting the union. Polls have so far shown both the Leave and Remain campaigns are deadlocked ahead of the referendum.

EU referendum Brexit Donald Tusk
European Council's President Donald Tusk and Prime Minister David Cameron seen together in this file photoReuters