Clocks in Northern Ireland face being one hour out from either London or Dublin if Brexit negotiations fail, peers have warned.

Brussels is planning to end the practice of changing the clocks twice a year after research found it was unpopular.

It would mean EU countries had to choose to adopt permanent summer or winter time, leaving Belfast potentially having to decide whether to align itself with clocks in the Republic or the rest of the UK, peers warned.

They said failing to secure an exit agreement would mean rules on the matter in relation to Northern Ireland would “fall away”.

“If the UK then decided to maintain summertime arrangements, Northern Ireland (assuming the devolved institutions have been re-established) would have to choose between having a one-hour time difference for half the year either with the Republic of Ireland or with the rest of the UK,” a report by a Lords committee said.

Although the changes are not due to come in until after the UK leaves on March 29 next year, the UK would have to adopt the measures during any transition period, peers said.

Current rules mean every state has to switch to summer time on the last Sunday of March and switch back to winter time on the last Sunday of October but the European Commission proposals would stop the practice.

EU countries fall into three timezones – Greenwich Mean Time, Central European Time and Eastern European Time.

The move would “not affect the choice of time zone” and it would “ultimately remain each member state’s decision whether to go for permanent summer or wintertime (or a different time)”, the proposals state.

European Commission President Jean-Claude Juncker has said millions “believe that in future, summer time should be year-round, and that’s what will happen”.

The move needs the support of all EU countries and backing from MEPs to become law.

In its report, peers on the EU Internal Market sub-committee, recommended the House of Lords issued a “reasoned opinion”, a mechanism that allows parliaments to register concerns about proposals.

They said the decision to end daylight saving clock changes should not be made by the EU.

The recommendation will be debated on Wednesday.

Committee chairman Lord Whitty said: “The European Commission’s proposal to end seasonal time changes goes beyond its remit and is not in compliance with the principle of subsidiarity.

“We are therefore recommending that the House of Lords issues a reasoned opinion.”