The discovery was made during a surprise three-day inspection of Stafford jail in May.

Inmates in two of the prison's wings fashioned strips of paper into planes, then attached lines to them and flew them over the 19ft perimeter wall.

The lines were then used to pull packages containing drugs and other banned substances back over the wall.

In a report published on Tuesday, Chief Inspector of Prisons Sir David Ramsbotham recommended that barriers be erected between the cells and the outer walls of the jail.

Sir David also criticised Stafford prison for being overcrowded and under-resourced and for failing properly to prepare inmates for life after they had served their sentences.