The new prison planned for Westbury is "devastating the community", says former long-serving Labor speaker Michael Polley who grew up in the town.
Mr Polley, 70, who was Tasmania's longest serving parliamentarian representing Lyons for more than 40 years, says his family moved to Westbury in the late 1800s.
"For four generations my family have lived at Westbury and this is devastating the community," he said.
"The community is overwhelmingly against it.
"I reckon of the people I've spoken to only one in seven would support it."
Mr Polley, who no longer lives at Westbury, said he was not playing politics on the location of the prison.
"This is a personal issue for me, not a political one," he stressed.
""It is my old home town and I have friends and relatives there and this is not the right place for a prison, the government has to look at another place for it."
Mr Polley's key concern was that house and land promises would drop because of the $270 million prison.
"I've been told that property prices could drop 25 per cent and that is devastating," he said.
"Even if it is a 10 per cent drop in value would you like that to happen to your property?
"Anyone putting their home on the market now is going to be up against it."
He was not able to provide an alternative site for a prison. That, he said, was up to the government.