'Brexit must not jeopardise peace in Ireland'

Britain’s most senior legal adviser in Europe has warned Brexit negotiators that peace in Ireland is fragile and must not be jeopardised by a botched border deal.

Eleanor Sharpston QC, an advocate general at the European Court of Justice (ECJ), said a common rule book between Northern Ireland and the Republic is vital to ensure frictionless trade.

In a rare address to journalists, the advocate general — who is also a member of the Irish Bar — dispensed with the ECJ’s customary legal discretion to offer a personal warning to negotiators.

She said: “Though we have had 20 years of the Good Friday Agreement, my senses — and my sense of talking to friends in the north and talking to friends in the south — is that though peace is there, its roots are maybe not quite as deep as one would like to be.

“Therefore, whatever the arrangement is for that border, it has to be a border which does not jeopardise what has been built over the last few years.”

Theresa May has pledged to end the jurisdiction of the ECJ when Britain leaves the European Union, but some have questioned how she can ensure frictionless trade on the island of Ireland without common rules.

A common rule book would effectively keep Northern Ireland in the single market and customs union, which follows the rules enforced by the ECJ, contradicting May’s plan to withdraw Britain from the jurisdiction of ECJ.

Sharpston said: “If you want to have frictionless trade it is necessary that a common rule book be interpreted in the same way on both sides of the invisible, therefore frictionless, border.

“As soon as you get divergent interpretations, you can no longer have frictionless trade.

“That’s a very simplistic, I hope actually rather uncontroversial, statement as a lawyer.

“What one does as a politician with that statement and that reality, I do not know.

“It is very evident that there is a problem called the border between Northern Ireland and the Republic.

“It is rather important for Ireland - and the island of Ireland - that the Good Friday Agreement holds.

“That agreement was ratified by plebiscites on the two sides of the border on the same day by crushing majorities, by majorities which were way in excess of the margin by which the 2016 referendum ended.”

Sharpston also warned that the legal implications of the Withdrawal Agreement, which is currently being thrashed out between London and Brussels negotiators, may not be fully understood by the time Britain leaves the EU on March 29.

“I spent a certain amount of my practising life at the bar explaining to national judges how EU law operated,” she said.

“They were on the whole very courteous, listened to me patiently, went away and read and grappled with the concepts.

“I do have a concern that the legal issues are rather complicated and that the amount of time available to understand them may not be as generous as it needs to be.”

The UK Department for Exiting the EU declined to comment.