Unions united yesterday against the coalition’s plans to sell off the justice system to the highest bidder.

New TUC research exposed the Con-Dem coalition’s plans to hand the most profitable 70 per cent of probation work and an ever-increasing number of prisoners over to shady private firms.

Already one in six inmates are held in privately run prisons, and with fewer staff combined with increasing overcrowding unions warn that the prison system is in meltdown.

In 2012-13, 29.3 per cent of prisoners in private jails were stuffed into overcrowded accommodation compared to 21.8 per cent in public prisons.

Prison Officers Association (POA) general secretary Steve Gillan said coalition cuts were hurting his members, who have to “work within an environment of violence and hostility due to the overcrowding caused by the government’s prison closure programme.”

The Justice for Sale report also called for a freeze in the privatisation of the probation service, currently set to be largely farmed out to the private sector by next year.

Con-Dem ministers claim that it will reduce reoffending and save money.

But probation union Napo general secretary Ian Lawrence condemned the “dangerous social experiment” which would see most of the service “sold off to the lowest bidders with little or no criminal justice experience.”

The report also flagged up concerns about electronic tagging schemes run by privateers and called for a thorough review.

G4S and Serco, two of the Ministry of Justice’s biggest contractors, are being investigated for overcharging the government by millions of pounds for such work.

TUC general secretary Frances O’Grady said: “It can’t be right that so much of our justice system should be placed in the hands of such a small number of private firms whose ultimate concern is shareholder profit rather than providing a good deal to taxpayers.”

GMB national secretary Brian Strutton said the “dogmatic” privatisation programme was “both reckless and dangerous” and that combined with cuts to legal aid services amounted to a “fundamental erosion of the entire system of justice in this country.”

And public-service union PCS general secretary Mark Serwotka said: “Without providing recourse to a fair, open and properly resourced justice system this country will lose the right to call itself civilised.”

Unite national officer Mike McCartney added: “You cannot put a price on an equal and just legal system, yet at every step that is what is happening, and it is happening without public debate about what is a cornerstone principle of a free, fair and participative democratic society.”