Some 2,300 sex offenders will be among the criminals whose supervision is outsourced to private contractors under government reforms to probation, it was claimed.
Around 3,200 gang members, 8,400 people convicted of domestic violence and 15,900 robbery cases are also among the "medium risk" offenders set for private supervision, the National Association of Probation Officers (Napo) said.
The public will be put at risk if such offenders are taken out of the care of the public sector and transferred to private firms such as G4S and Serco, the union said.
Speaking yesterday, Napo general secretary Harry Fletcher said: "The Government's plans are both chaotic and dangerous."
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