The order appears to directly contradict claims by the prison service that everybody is searched when going into a prison - "even the Home Secretary".
The claim was made last month after complaints by probation officers that they were being harrassed with intrusive physical searches when visiting jails to interview clients.
The Independent has discovered, however, that prison gate staff have been told not to search any senior officials from prison service headquarters or even require them to pass through security X-ray equipment.
A memo sent to the gate staff at HMP Birmingham, by Tom Watson, the jail's head of security, states: "The governing governor has instructed that senior prison service personnel (eg, director-general, directors, members of the prisons board, area managers etc) will NOT be required to pass through the X-ray portal when entering or leaving the prison."
The memo was sent out on 27 November, only weeks before Richard Tilt, director-general of the prison service, claimed that no-one was allowed to be an exception to the rules on security.
Staff at the jail said last night that prison officers had been reprimanded last November after they insisted on searching Dai Curtis, a prisons area manager, and taking possession of his mobile telephone while he was in the jail.
They said that Ann Widdecombe, the prisons minister, had been allowed to drive into the jail in October without a search.
Last night, Bev Lord, vice-chairman of the Prison Officers' Association(POA), said: "This memo shows the astonishing double-standards of those running the prison service.
"By making themselves exceptions to the rule, they are placing staff in an impossible position and putting security at risk."
She said staff at other jails were put under similar pressure to give special treatment to prison management.
An officer at Birmingham prison, said: "The staff here feel let down. Everybody should be searched and there should be no exceptions at all."
Harry Fletcher, deputy general secretary of the National Association of Probation Officers, said: "This confirms that the searching is discriminatory.
"The whole management hierarchy have made themselves exempt. It is highly hypo- critical."
Later this week, NAPO's lawyers will decide whether probation officers can sue the prison service for assault in relation to some of the most intrusive searches.
More than 70 probation staff have complained about the "rub-down" searches by staff, which have included examinations of ears, mouths, hair, inside legs, shoes, bras and waistbands.
The Independent has also learned that no prison official is to be disciplined over the early release fiasco last autumn when 541 prisoners were allowed out of jail early after a blunder in calculating their sentences.
A letter by Mr Tilt, to David Evans, general secretary of the POA, states: "I have interviewed eight members of staff in connection with the issue ... the purpose of these interviews was to explore the lessons which could be learned for the future from these events."
Mr Tilt said that he had written to each of the eight, "drawing to their attention any shortfalls in their performance". He said that he would not be taking further action.Reuse content