Northern Ireland footballers must carry British passports or risk being barred from playing for the country, it was confirmed yesterday.

Fifa said rules on dual nationality which allow people in Northern Ireland to carry two passports do not apply to players when they are on the pitch.

The clarification prompted the Irish Football Association (IFA) to warn its footballers they face being disqualified from competition if they refuse to comply.

An IFA spokeswoman said Northern Ireland footballers, at all levels, can travel on whatever identification they choose but must produce a British passport for match officials if they wish to line out for the team.

"We are taking Fifa on its word and we are accepting their decision," she said. "I think Fifa made it clear that their decision is finalised and they have gone to an awful lot of work to investigate the issue." She insisted it was always IFA policy to inform players being called up to squads that they needed a British passport.

The controversy has caused a political storm with nationalists insisting it is contrary to the tenets of the Good Friday Agreement which gives citizens in the North the right to hold dual nationality. Last week Celtic midfielder Neil Lennon branded the rule ridiculous and said it would have barred him from playing.

He said: "(It) would have ruled me out for a start. The fact is that if you're from Northern Ireland you're Irish. It's a ridiculous move." Lennon has retired from international football following death threats from loyalists.

Two Derry City players were sent letters from the IFA reminding them they must carry a British passport for the May 10th under-21 match between Northern Ireland and Liechtenstein.

At least one of them was understood to have refused to co-operate prompting the clarification from Fifa. Their officials wrote to the IFA at the beginning of the week to clear up any confusion.

In a letter to IFA chief executive Howard Wells, it said: "Fifa sees no alternative but to require players to hold the passport of the national association they are seeking to represent in order to allow the match commissioner to verify their eligibility.

"The fact that a player holds an Irish Republic passport does not demonstrate conclusively, that he or she is eligible to play for Northern Ireland."