The seven-page report by Jim Bennett outlines his experiences at Estyn. He sent it to chief inspector Susan Lewis and her colleagues prior to leaving the service this July, but now the highly-damaging document has been leaked to the Welsh Assembly, teacher unions and The TES.

Mr Bennett condemned Estyn as “a tall hierarchy with a remote chief inspector” and said: “Since joining Estyn more than two years ago I have spoken to the chief inspector only twice.”

He added: “Inspectors are expected to do jobs for which they are unqualified. I have done inspections in retail and customer care, caring and health (as lead inspector) and careers in schools, all without training, or even initial briefing.

“If you don’t understand the detail, you cannot inspect something rigorously, or offer useful advice in the process. It shows in the quality of the reports written.”

He also expressed concern that Estyn does not have a quality control system and said: “We insist that all the institutions we inspect have a fully developed one. The few quality processes that do exist are not effective. Inaccurate judgments may sometimes by challenged but are seldom, if ever, changed. There are no mechanisms for ensuring consistency of judgments”.

Mr Bennett, now assistant principal at Llandrillo College in north Wales, was dismayed to hear the document had been leaked. He said: “They were private comments for colleagues.”

An Estyn spokesman said: “This refers to an internal matter that was dealt with at the time.”

The Welsh Assembly, which monitors Estyn’s work, refused to comment on the document because it had been sent anonymously.

Gethin Lewis, secretary of the National Union of Teachers Wales, said: “We have a number of concerns with Estyn and these are similar to those that have been outlined in the letter.”

Susan Lewis has been chief inspector of Estyn for five years . Her contract is to end in June 2002. An independent panel will meet in January to decide whether her contract will be renewed for another five-year term.