A bar in Uplands shouldn't have been altered to allow customers upstairs, council planning officers have said.
Changes were made at Jack Murphys bar-restaurant last year to accommodate customers on the first floor - mainly on a rear-facing rooftop terrace.
Bosses at the Uplands Crescent venue said this internal work didn't constitute development and that the first floor of the building - which they said was office and storage space - had historically been used as part of the ground floor.
They also said the rooftop terrace was set well back and did not adversely affect the building's appearance or that of the Uplands Conservation Area.
There is a flat on the second floor and, more recently, additional customer toilets.
But Swansea planning officers said the first floor had a different use as residential.
They described the alterations as an "intensification" of the ground floor into the upper floors.
Officers also said new fencing and a fire escape on the first floor constituted development.
They turned down the certificate of lawfulness application, and said planning permission for the work that had been carried out was needed.
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The ground floor of the building used to be home to the restaurant Wasabi.
Jack Murphys was the latest bar-restaurant to open along Uplands Crescent, which has become a very popular spot for an evening out and day-time coffees.
Planning officers have curbed their spread in recent months.
In February, a proposal to convert the former Dixey's opticians into a licensed restaurant-bar was rejected.
The council also turned down an application last month to convert the former NatWest branch into a bar-restaurant.
In both these instances, the applicants said there had been no or virtually no interest from retailers and that their proposals would have created jobs and brought empty buildings back into use.
But planning officers said the increase in such venues was undermining the retail function of the designated Uplands District Centre.
Some residents have also objected to what they feel is an over-intensification of bars, and associated disturbance and noise.
Uplands councillor Irene Mann said the section of Uplands in question was both a conservation and residential area.
"I'm very glad to see the planning officers have taken a tough line," she said.
