Cura said Manx Radio Gold, launched in July 2024, had “attracted complaints and scrutiny” over its impact on the overall speech content.
The regulator said the service was not considered distinct enough from the main station to need a separate licence but that meant it was treated as part of the station’s overall output.
Analysis carried out by the authority ahead of further planned consultation had “caused concern” the speech level was not as high as required.
It said while that had been shared with the station, which had been “invited to suggest remedies that could be put in place”, there had been “no progress towards resolving this matter”.
The authority said it therefore “has little choice but to treat the matter as a potential licence compliance issue”.
Although the investigation was currently limited to determining if the speech requirements were being met, the regulator said it reserved “its right to investigate any additional matters that may arise during the course of the investigation”.