An Post is reportedly seeking legal advice after discovering that several Irish companies are using the British postal system to send mail to Ireland in order to avail of cheaper rates.
The Irish companies transfer their mail to Britain, where it is then posted back to Ireland by Royal Mail.
The companies are reportedly making savings of around 25% because of the move.
However, An Post has claimed that, under the law, post originating in Ireland must be put through the Irish postal system.