DUBLIN (Reuters) - It is too late to tweak the Irish “backstop” mechanism in Britain’s EU withdrawal agreement, a senior Irish minister said on Wednesday after several candidates to replace British Prime Minister Theresa May said it must be changed.

FILE PHOTO: Ireland's Minister for Finance and Public Expenditure Paschal Donohoe arrives at a European Financial Forum event in Dublin, Ireland February 13, 2019. REUTERS/Clodagh Kilcoyne

The backstop, which requires Britain to adopt some EU rules indefinitely unless a future arrangement is found to keep open the land border between Northern Ireland and Ireland, was the key reason May failed to secure parliamentary backing for her withdrawal deal.

Asked if there was any chance at all of tweaking the backstop, Irish Finance Minister Paschal Donohoe said the European Union and several of its leaders had made clear this week that the divorce agreement would not be opened again.

“If anyone in the UK involved in this process... had a better idea than the backstop, then they have had many years to table that idea,” he told journalists in Dublin.

“If there is consensus that we do not want to see the return of a hard border on the island of Ireland... all paths do lead back to the backstop,” he said.

Asked if an earlier alternate arrangement that would see the EU rules only adopted in Northern Ireland might be acceptable now, Donohoe repeated that the terms of the deal had been agreed.

The Northern Ireland only backstop option was rejected by the Northern Irish Democratic Unionist Party, whose 10 members of parliament the British government needs to pass legislation.

Donohoe said the Irish government was aware that many candidates for May’s job appeared open to leaving the European Union without a deal, which would have “many serious consequences” for Ireland.

But he said Dublin had no choice but to let the process conclude within the United Kingdom.

Britain will automatically leave the EU on Oct. 31 without an agreement unless parliament approves one first, the EU grants an extension, or the government revokes its decision to leave.