NORTHERN Ireland has the right to leave the United Kingdom and join the European Union as part of the Republic after Brexit, ministers have conceded for the first time.

In a fresh blow to Theresa May’s efforts to keep the Union together, ministers have concluded that the country would not have to reapply for EU membership as a new state if it voted for reunification.

The British Government’s position was revealed in a letter from David Davis, the Brexit Secretary, to the SDLP MP Mark Durkan. Davis conceded that the British Government is bound by the terms of the Good Friday Agreement, which set in place a mechanism for reunification — should a majority of voters in both countries agree to it.

“If a majority of the people of Northern Ireland was ever to vote to become part of a united Ireland, the UK Government will honour its commitment to enable that to happen,” he wrote.

“In that event, Northern Ireland would be in a position of becoming part of an existing EU member state, rather than seeking to join the EU as a new independent state.”

Davis added it would be up to the European Commission to set out the “procedural requirements” for that to happen. Davis’s statement was made after discussions with Northern Ireland Secretary James Brokenshire. A senior government source confirmed that it was the first time ministers had set out the British position.

Ministers and government lawyers are understood to have concluded that the situation in Northern Ireland is akin to that in Germany before reunification. When East Germany joined together with West Germany in 1990 it automatically joined the European Community — the forerunner to the EU. This would mean Northern Ireland would have to adopt the euro, the currency used in the Irish Republic.

A similar mechanism that would allow a united Ireland to be in the EU, has also been raised by MEPs as a way an independent Scotland could remain in the EU. However, in Scotland’s case the scenario would be the member state contracting rather than expanding.

Davis added it would be up to the European Commission to set out the “procedural requirements” for that to happen.

His letter to Durkan makes clear that the British Government position remains “to support Northern Ireland’s current constitutional status”. It added: “We are committed to the principle of consent enshrined in the Belfast Agreement which makes clear that Northern Ireland’s constitutional position is a matter for the people of Northern Ireland to determine.”

Durkan said he had been trying to force the Government to clarify its position but that it had “avoided it up until now”.

He said: “There must be no misunderstandings about this. While the Government has acknowledged the special status of Northern Ireland, the UK now needs to join the Republic in calling for this to be made clear in any final Brexit agreement.”

The letter emerged as civil servants were preparing to take control of the Belfast’s administration budget from tomorrow after the failure of political parties in Belfast to restore power sharing.

In the Commons yesterday, Brokenshire said the UK Government will “consider all options”

after Easter, including direct rule, if continued talks to form a Northern Ireland Executive fail.

Brokenshire said the Government “did not want to see a return to direct rule”. But, in the absence of a devolved assembly, he added, it is up to the Government to provide “political stability”.

On Monday, he said there is a short window of opportunity for the talks and removed the prospect of a second snap election within weeks.

Under the terms of the Good Friday Agreement of 1998 the British Government is legally obliged to offer Irish voters a referendum on reuniting the country within the EU should polls show support for the plan. Northern Ireland voted to remain in the EU last June by 56 per cent to 44 per cent.

While pre-Brexit polls have shown little support for reunification, senior UK Government sources believe the issue could re-emerge in the event of a hard Brexit adversely affecting Northern Ireland’s interlinked economy.

In the Republic, Fianna Fail and the Labour Party have both said the country must start preparing for a united Ireland.