RTÉ and TG4 try to buy sports rights on an all-island basis but Ofcom says that in practical terms that is rarely possible.
It said: “In many cases international sporting organisations and their agents sell separate packages for the UK and the Republic of Ireland.
“Northern Ireland is normally included within the UK package.
“Bespoke arrangements for NI are not always available commercially. Where an alternative arrangement is available, the additional cost may be disproportionate for relatively small public service broadcasters.”
In addition, it said the way in which IP addresses are currently managed means geolocation databases cannot reliably distinguish a Northern Ireland user from one in Great Britain.
Ofcom has suggested that a first step to any solution would be for the British and Irish governments to review their 2010 Memorandum of Understanding which covered cross-border access to digital terrestrial TV.
That agreement was about making sure BBC channels could be easily received in the Republic and RTÉ/TG4 in Northern Ireland via terrestrial signals.
Ofcom said a review could assess whether its scope should cover IP-delivered services as well as digital terrestrial TV.
The economy minister said the geo-blocking of RTÉ content is “completely unacceptable and must be brought to an end”.
She has asked the governments to start the review suggested by Ofcom.
“I have written again to the British and Irish governments to seek their engagement and cooperation on resolving this issue once and for all,” she said.