The first permanent property being built on a gypsy/travellers’ site at Holbeach has breached its planning permission.
South Holland District Council gave consent last November for William Gaskin to build a dayroom at Rose View Drive, but part of the property is not as agreed.
A council spokesman said: “We are aware that windows in the gable ends of the building are not in accordance with the approved plans and this issue has been raised with the applicant via his agent.
“We will take action against any applicant that does not comply with planning regulations.”
A previous application by Mr Gaskin for a replacement dwelling for a static caravan was turned down because the council did not want to set a precedent for permanent dwellings and it would have gone against planning policy. But after discussions with other local planning authorities, an agreement was reached.
A condition attached to permission for the dayroom is that it is only used as additional living space and never as sleeping accommodation.
The whole site was developed to end an unauthorised encampment at Cranmore Lane. The £1million project was dogged with problems before occupants finally moved on to the ten-pitch site in June 2011.