More than £10m was spent updating a Suffolk prison in the three years leading up to its closure, an independent monitoring board has revealed.
HMP Blundeston, near Lowestoft, closed in December last year and the property was handed back to the Ministry of Justice last month.
In September 2013, the government announced plans to replace the jail, and others, with two so-called "super prisons". Ministers said HMP Blundeston was no longer fit for purpose and would cost too much to bring it up to standard.
But in its final report, the prison's Independent Monitoring Board (IMB) has revealed more than £10m had been spent on the prison in the three years leading up to that announcement.
The money was used for new heating and roofs, and a new laundry which was due to take on the task for a number of prisons in the eastern region.
New equipment for the welding shop is reported to have cost £80,000 but was never used while a computerised key-issuing system was installed just one month before the government revealed the plans to close the prison.
The IMB said there were also many more costs involved in closing Blundeston, including redundancy payments and re-location of staff.
Former Waveney MP Bob Blizzard today said he believed the decision to close the prison was been political.
The IMB's report said HMP Blundeston was a good, local prison with strong rehabilitation programmes and a good relationship between staff and prisoners.
Brian Cadman, who was the longest-serving member of the board, said: "The IMB, formerly the Board of Visitors, would like thank all the governors and staff at HMP Blundeston for all their help and support over the past 50 years of operation and praise those staff for all that they have achieved in protecting the public and working to rehabilitate prisoners.
"We have great respect for the work you have done and what you have achieved can never be taken away."
The Ministry of Justice said the decision to close was taken by senior managers. Axing it and three others was intended to save £30 million a year.