The abuse of Northern Ireland's healthcare system by patients from the Republic has the potential to damage services here, a leading GP has said.
His comments come after this newspaper revealed the number of medical cards registered in Northern Ireland is up to 80,000 higher than the number of people who live here – currently around 1.8m.
While there may be some discrepancy in numbers because of people moving away and students from Northern Ireland living elsewhere, it's thought the number is largely inflated by people who live in the Republic – where healthcare is not free – who have managed to secure a medical card through an address in the north.
Last night, Dr Black explained that a number of factors account for the startling 80,000 figure, but stressed the main problem is patients from the Republic inappropriately accessing healthcare in Northern Ireland.
"We are definitely aware of the fact that there are more patients registered than there are people who live in the area," he said.
"Some of that is due to cross-border workers, who live in the Republic of Ireland, work in Northern Ireland and are eligible. Also, patients register with their next doctor before leaving their previous doctor.
"A large part of what is happening is patients living outside the jurisdiction availing of services inappropriately in Northern Ireland."
Documents seen by the Belfast Telegraph revealed there were 16 people registered to one two-bedroom house in south Armagh.
Dr Black said the feeling in the GP community is that "genuine patients" from Northern Ireland could suffer.
"I don't think it is reasonable to register in Northern Ireland if you are not eligible to be a patient in Northern Ireland," he said.
"The main problem is funding follows the population of the area, not the GP registered population.
"In other words if you have too many patients registered inappropriately you won't have funding for the genuine patients from Northern Ireland."
Patients in the Republic pay €40-€60 (£33-£50) to see a GP in the Republic and are then subject to pharmacy costs.
Dr Black told the Belfast Telegraph an asthma inhaler would cost a patient in the Republic around £40, whereas prescriptions in Northern Ireland are free.