More than £56 million of public money was spent on redundancy payments to prison staff in England and Wales in one year, a minister has said.
The severance bill for prison staff in 2013 was £56.5m, compared with £5.7m in 2012 and £4.1m in 2011.
Frances Crook, chief executive of the Howard League for Penal Reform, said it had been a "massive waste" of money.
But Prisons Minister Andrew Selous said major organisational change had created "significant savings" for the taxpayer.
The figures were disclosed by Mr Selous in response to a Parliamentary question from Labour MP, Jenny Chapman.
He said the figures for 2013 were higher because voluntary early departure schemes had been available in large numbers during the year.
"We have managed major organisational change in the last year to create significant savings for the taxpayer and ensure the best use of public funds," he said.
"In January 2013 there were in excess of 6,800 empty beds in prison, costing the taxpayer around £190m per year. This could not continue."
Mr Selous said government reforms were "delivering value for money for the public purse while optimising skills through new ways of working and putting all officers in prisoner-facing roles".
The changes would save £300m a year from prison budgets by 2015/16, he said.
BBC home affairs correspondent Danny Shaw said the number of prison officers, governors and support staff in public sector jails had fallen by 10,000 since 2010 - with half of the jobs going since 2013.
Some prisons have had to recruit former prison officers and use officers from other establishments due to staff shortages, our correspondent said.
Prison inspectors and other experts have said staffing problems have contributed to a worsening performance of a number of jails, although a major recruitment and training exercise is ongoing with 1,700 new prison officers due to be in place by April.
Mrs Crook said "mismanagement" of the prison system had been "breathtaking" and had resulted in a "massive waste of public money".
"Whilst prisons sank into an abyss of violence, gangs, suicides and criminality, ministers clearly panicked and are now desperate to recruit new staff to replace the experienced people they got rid of," she added.
The Howard League for Penal Reform has previously said the prison system in England and Wales is "in crisis".
Labour has previously accused the government of "closing down too many prisons too fast and cutting staff while the number of prisoners has gone up".