Almost one in ten NSW Corrective Services staff faced professional misconduct hearings last year, it is being reported.

The Daily Telegraph obtained documents under Freedom of Information laws showing 316 of the 554 complaints against employees were investigated further after officers were accused of mistakenly releasing inmates, trafficking contraband, sexual assault and failing drug tests.

Twenty-four officers were later disciplined for "improper relationships" with former or current inmates, 28 were censured for harassing other staff members, 22 failed drug and alcohol tests and four were caught trafficking contraband, the newspaper reported.

The documents also show 35 of the 471 cases heard by the Professional Conduct Management Committee in the 2007 financial year were being investigated by police for non-work related matters.

Twenty-five of those cases involved shoplifting, assault and firearms offences.