The remains of 42 bodies with hands tied behind their backs have been found buried in shallow graves on a building site.
It is thought the skeletons, found on former farmland in Buckingham, could date from Anglo Saxon times or or possibly even be criminals who were hanged on the gallows.
Brio Retirement Living Holdings, which is developing the land to retirement flats, has been accused of not declaring the discovery of the bodies by local historians and residents.
The company finally won an appeal last year after years planning permission argument.
Brio, which is part of property management company Places for People commissioned an archaeological investigation of the site as a condition of winning planning permission.
The 42 bodies were discovered several weeks ago yet nobody including Bucks County Council's Archaeological Service (BCAS) has yet seen the archaeologists' report.
District and town councillor Robin Stuchbury said: “This find is of great historical significance to Buckingham and it should not be hushed up.
“I am aware that the bodies were found in December.
"There were more than 40 of them and they had their hands bound behind their backs, which infers they were prisoners of some kind.
“They could date from Anglo Saxon times, when there were killings in Buckingham, or from during the Civil War, which also saw casualties. Or they could be criminals who were hanged on the gallows in the town.
“The fact is, we have a right to know. This is part of our history.”
The skeletons have since been removed, leaving just empty holes in the ground that were their graves.
It is not known whether there were any artefacts buried with them that could help date the time of their deaths.
A spokesman for Bucks County Council said: “We are unable to comment on the archaeological remains discovered at the West End Farm site at present, as we are still awaiting a report detailing the results from the archaeological contractors.”
Places for People have been approached for comment.
