Persistent offenders between 12 and 14 can also be put into a locked room alone overnight and strip searches can be carried out without recording a reason.
The regulations covering the five secure training units, which are the centrepiece of the Criminal Justice Bill, were disclosed yesterday.
The Howard League for Penal Reform said the rules would break the 1989 Children Act. It also claims untrained security staff could be left to carry out strip searches.
The Home Office strongly defended the procedures and argued that most of the practices were carried out at existing secure accommodation units. They also insisted that all staff would be properly trained.
The specifications for the units, which will cost pounds 30m and hold about 200 young people, will be sent to private companies wishing to make a tender.
The regulations, disclosed by the Howard League, allow staff to read children's letters and stop them if they are too long. Visits from families can be stopped and no outside groups such as journalists may visit without the Home Secretary's permission.
All strip searches must be made by more than one member of staff of the same sex and only after the most senior officer on duty has given permission.
Frances Crook, director of the league, said: 'The jails for young children will allow staff to abuse children sexually and physically, hidden from outside scrutiny. The inevitable result will be a tragedy.'
Government plans for the secure training centres were thrown into confusion two weeks ago when the House of Lords voted for amendments to the Criminal Justice Bill.
These gave magistrates the option of sending young offenders to local authority secure units rather than the new institutions. The second amendment allowed young offenders to swap to or from the new secure units in the middle of their sentences.
The Government is still considering whether or not to accept the amendments, which have forced them to delay the Bill until the autumn.
David Maclean, a Home Office minister, said: 'This is a sordid and scurrilous attack which scrapes the bottom of the barrel of political scaremongering.
'There will be high-quality training and education provided by professional and highly trained staff and monitored by independent inspectors, so that peristent juvenile offenders can mend their ways.'