Oxford's FM 107.9, which is available on FM in Oxfordshire and online, currently broadcasts a music-heavy schedule aimed at 15 to 29-year-olds.
However, Passion Radio Oxford (PRO) requested to change the station's schedule and target audience to an "easy listening soft music service aimed at a 45-plus audience".
Ofcom agreed to consider the request on June 16, but subsequently decided that it was necessary to launch a public consultation on the proposal.
The media regulator received 96 responses to the consultation, with just five in favour of the change and 91 against it.
Ofcom has the power to approve format changes for analogue commercial radio stations in accordance with Section 106 (1A) of the Broadcasting Act 1990.
However, the watchdog's Radio Licensing Committee said that it was not satisfied with the conditions of the change and therefore declined PRO's request.
"In particular, the committee believed that the move to target the service at an older audience which is also being served by other relevant independent stations in the area, while ceasing to serve the under-30 population, would have the effect of narrowing the range of programmes available," said Ofcom.
"There was also no evidence of significant demand for, or support for, the proposed change."