Mr Bloomer was mounting a vigorous and lengthy assault on unions he accused of misusing equal pay legislation to pursue salary rises. “They are essentially regrading claims masquerading as equal pay cases,” he said.

Strathclyde’s former depute director in charge of staffing warned the conference of the implications of the case in which the Scottish Secondary Teachers’ Association successfully argued before an industrial tribunal and subsequently in court that Dorothy Tedman, a teacher at Carluke High, was doing the job of a principal teacher because she was effectively running the computing department but not being paid as such. She used a male as a comparator.

The result of Mrs Tedman’s victory is that 475 equal pay cases are outstanding against the 12 former Strathclyde authorities with several hundred waiting on the outcome.

The most notable of these is the Wallace case which the SSTA, helped by the Equal Opportunities Commission, is taking to the House of Lords on behalf of nine members. The Marshall case, shortly to go before the Court of Session, involves special school instructors claiming parity with teachers. Nursery nurses and outdoor centre staff are also pressing for comparable levels of pay.

The cases are being pursued under the 1970 Equal Pay Act, Mr Bloomer said, “yet not a single claimant has ever suggested they were victims of discrimination, and the pay arrangements in place in Scotland are self-evidently not discriminatory.”

The lesson from the Marshall case, he said, was that tribunals are not interested in curriculum-speak or formal qualifications but in the nature of the work. “What emerged in that case was considerable overlap between jobs and job descriptions which were very weak,” Mr Bloomer said. “Some instructors were even called ‘educators’ which was an attempt to draw them into the work of the school but which was absolutely fatal to Strathclyde’s case at the tribunal. ”

Strathclyde’s successor councils face a bill for Pounds 90 million if they lose, and others would be entitled to recompense on the back of such a decision. Mr Bloomer said there could be further ramifications if principal teachers of large departments sought higher salaries, and even claims by workers such as architectural technicians that they were doing the work of architects.

The Pounds 90 million would equal all the cuts made by Strathclyde Region in its last five years and, if the other cases triumph, the effect would be the equivalent of wiping out the extra penny on income tax the Liberal Democrats say should be used to boost education.

Mr Bloomer concluded: “In the era of devolved school management it becomes more and more important for heads and deputes to be aware of such problems. In Strathclyde, it was not the authority’s policies that were at fault. Something, however, went badly wrong when it came to decisions taken in individual schools which we discovered later had largely ignored advice I had sent out following the Tedman case.

“Schools must therefore ensure they are equal pay proof.”