RTE says it is considering legal action over a plan by Cable Management Ireland to place TV3 on the channel previously used by Network 2.
CMI, which provides cable television to 65,000 subscribers, has decided to move RTE's Network 2 to channel 7, away from channel 2, where it will place TV3.
RTE has communicated its concern at the move to the Director of Telecommunications Regulations, Ms Etain Doyle.
In its letter to Ms Doyle, the managing director of organisation and development, Mr Liam Miller, says RTE sees no "logical or technical reason why this particular reallocation of frequencies should take place".
RTE has advertised in newspapers in Co Kildare, where CMI has subscribers, telling readers of the changes as it fears they may not be able to tune in to the All-Ireland football final next weekend between Kildare and Galway.
An RTE spokesman said this would cause undoubted distress to viewers. RTE was considering its options, including legal action, he said.
CMI has customers in Naas, Celbridge, Newbridge, Maynooth, Athlone, Tullamore, Mullingar, Sligo, Donegal, Ballina, Buncrana, Arklow, Wicklow, Greystones, Dundrum, Enniscorthy, New Ross, Carlow, Portlaoise, Tullow, Swords, Malahide, Ashbourne, Rush and Navan.
According to CMI's managing director, Mr Ray Doyle, TV3 is the first Irish alternative to RTE, and it was right and fair that it be given prominence. RTE 1 will still be the first channel and TV3 will be next. He said he did not want to move the four British channels as they were the vehicle that drove subscriptions for cable operators.
An RTE statement said that while it was understood changes in channel allocation were necessary to accommodate the increased number of services these could have been made without affecting RTE. CMI's decision, it said, was an "unwarranted disruption of our service".