Taoiseach warned 'core of the dispute' with UK was backstop
The EU's former negotiator in the war in Bosnia warned Taoiseach Leo Varadkar about the Brexit backstop to avoid a hard border in Ireland.
Lord David Owen wrote to Mr Varadkar saying the backstop could represent a "basic contradiction" in the Brexit deal between then-Prime Minister Theresa May and the EU.
He added that it is "at the core of the dispute between our countries".
New Prime Minister Boris Johnson is demanding that the backstop be scrapped, but this has been met with refusal by the EU and Ireland.
The intervention by Mr Owen, who was the EU's negotiator in the Balkans from 1992-95, came after the original March 31 deadline for Brexit was missed.
His letter to Mr Varadkar was released under Freedom of Information laws.
He wrote: "I wish to urge you to carefully consider a possible basic contradiction within the EU-UK Withdrawal Treaty which has so far prevented a majority of British MPs approving it in its present form."
The letter says Attorney General Geoffrey Cox had determined that the terms of the agreement "could prevent the UK from ever leaving the Irish backstop".
Mr Owen adds: "Unless this potential basic legal contradiction is grappled with at the highest political level it is hard to see the Withdrawal Treaty being agreed."
Mr Owen suggested the European Court of Justice could consider the issue of the backstop.