Light from Swansea City AFC's training ground is preventing the night sky above Gower from being granted special protection, it has been claimed.
Environmental group Gower Society has drawn up a list of organisations with lighting systems which "annoy" stargazers.
It claims light pollution is stopping the Gower Peninsula from being awarded dark sky status.
A Swans spokesman said the club was working to sort out lighting concerns.
The society's list includes farms, caravan parks and a number of rugby grounds as well as the Swans' training ground at Fairwood.
It claimed the sites do not comply with Swansea council's efforts to control light pollution.
But Gower Society chairman Robin Kirby said it has received a sympathetic hearing from the Swans.
"In fairness they are looking at it, they are treating it seriously," he said.
The council said that although Gower was not currently a dark sky designated zone, a survey carried out some years ago suggested that it could become one, if problems are sorted out.