The Government is to ask customers whether they will agree to a rise in letter and other postal charges.
An Post, currently confronted by heavy losses, has requested approval for an increase in the price of letter stamps of three cents to 41 cents.
But telecommunications regulator Ms Etain Doyle ruled tonight that the application should be subjected to a public consultation process.
She said: "The intention is to ensure that An post cannot use its monopoly position to increase prices unreasonably and cross-subsidise activities in the non-reserved area where it does face competition."
Ms Doyle said the An Post application would allow for cost decreases in certain cases.
She said: "The company is facing a significant operating deficit on the postal services, and although it has a cash surplus that can cushion the impact of losses for some time, it must achieve substantial efficiencies to face full competition in the future.
"It is clear they will have to make substantial changes in the way they price their services."
PA