Probation officers took to the streets at lunchtime as Con-Dem ministers slap the latest "For Sale" sign on to Britain's justice system.

Hundreds of picket lines will form outside probation offices across Britain in protest at plans to flog off 70 per cent of the service to dodgy security privateers.

Members of Napo, Unison and GMB members across England and Wales walked out as the Official Journal of the European Union prints a Ministry of Justice (MoJ) advertisement inviting firms to bid for contracts.

Justice Secretary Chris Grayling claims that profit-making companies will curb crime by providing extra support to released prisoners and plug a "huge gap in the system."

He plans to turn people deemed to be of "low and medium risk" over to privateers.

But the probation service's 18,000 workers warn that Mr Grayling's plan will threaten jobs and will fail to give released offenders the support they need - putting the public at risk.

Probation union Napo general secretary Ian Lawrence warned: "If it's not bad enough that this government doesn't care about jobs, professionalism and people's livelihoods, not caring about public safety is a downright disgrace and a total failure on their part to fulfil their duty to society."

Unison general secretary Dave Prentis said that the coalition was trying to "wash its hands of any responsibility for maintaining a safe and efficient probation service."

And GMB national officer Sharon Holder said the government wanted to "privatise the local probation service at all costs" in an "ideological, politically motivated" decision that won't benefit the public.

"Privatisation will axe services that keep our communities safe," she said. "It will transfer work to private companies interested only in profit.

"The citizens of this country could be in danger as a result."

Ministers plan to close 35 local probation trusts in March next year and replace them with a single centrally run service responsible for high-risk offenders.

The remaining 70 per cent of the service will be moved into 21 "community rehabilitation" companies which will be sold to private companies after six months.

High on the list of likely bidders are Serco and G4S - both currently under investigation for alleged fraud relating to previous MoJ contracts.

"If one of our members was under investigation for fraud, they would be suspended immediately," said Mr Lawrence.

"Yet Grayling seems to think it's perfectly alright for G4S and Serco to remain in the ring and prepare to bid for yet another public-sector contract."