The nearly-finished George Reynolds Centre has been compared to the Berlin Wall by a campaigner who tried to stop it being built on the Henhayes Recreation Ground.
Betty Spanswick is a former town councillor and was part of the Friends of Henhayes group which tried to prevent the green space being built on.
As the sports and community centre nears completion, she says her fears have been realised as the building cuts off the green public space from the rest of the town.
Mrs Spanswick said: “This demonstrates clearly what the Friends of Henhayes were trying to prevent when they attempted to register the Henhayes as a town green to prevent development.
“I find it difficult to understand how South Somerset District could justify blatantly ignoring the advice of their professional planning officers by allowing permission for this ugly new building to be built where it is. There were other options but their minds were made up.
“As the Friends warned, the view of the magnificent Lucombe oak tree is completely obstructed by this ugly building and the leisure field hidden behind what is virtually a brick wall.
“Whether that brave old tree will survive the latest onslaught no one knows.”
The sports and community centre was granted planning permission, against officers’ recommendations, in November 2009.
The £825,000 centre will be home to the town’s rugby, football and cricket clubs as well as current users of the West One Centre, including a youth club, play group, after-school group and creche.
Members of the Friends of Henhayes said they were not against the centre being built, just the location.
Mrs Spanswick added: “I don’t want to stop anyone playing games but the field is now cut off from the town. It is like the Berlin Wall.
“I have some new neighbours who did not even realise it was a public recreation ground.
“People are not always aware that these things are happening until it is too late. We tried to make the town aware at the time but some are probably only just realising what is happening.
“I think if the town had put more thought into it, an alternative site could have been found.”
The George Reynolds Centre is due to officially open in the next few weeks.