Strathclyde’s 12 successor authorities are braced for a massive pay-out to upgrade 297 secondary staff to principal teachers’ salary levels after the region suffered its second major court defeat last week.

The decision by the Employment Appeal Tribunal, headed by Lord Coulsfield, to uphold the earlier verdict of an industrial tribunal, is likely to have profound consequences for already overstretched budgets. Glasgow City Council may have to find Pounds 5 million in back pay for 102 staff and South Lanarkshire Pounds 2.2 million for 44 staff.

The total bill could be as high as Pounds 20 million, and the annual salaries bill could rise by Pounds 2.7 million.

North Lanarkshire and Renfrewshire may have to find more than Pounds 1. 5 million each. North Ayrshire, East Renfrewshire and Inverclyde could face bills of more than Pounds 500,000. South Ayrshire has the smallest potential bill, at under Pounds 100,000. All other Scottish councils, with the exception of Grampian and its successor authorities, will be affected by the outcome.

Strathclyde is prepared to take its case to the Court of Session and ultimately to the House of Lords because of the sums involved. Linda Marsh, assistant director of education, said: “We owe it to our successor authorities. ”

The Scottish Secondary Teachers’ Association, which began the action in 1991 on behalf of 10 women staff, hailed the judgment as a “triumph for fairness”. Alan Lamont, the union’s general secretary, said: “If they had done the reasonable thing from the outset, there would not have been the accumulation of the sums of money there is now.” The union lodged a claim under the Equal Pay Act but it was only in April last year that an industrial tribunal ruled in favour of SSTA members.

Strathclyde then appealed on legal grounds. It intends to pursue its argument that the Equal Pay Act, which focuses on sex discrimination, was not a proper mechanism for bringing the case.

Ms Marsh confirmed that with five years’ back pay, plus interest at 8 per cent, many teachers could be owed Pounds 30,000, and some up to Pounds 50,000. The region hopes to persuade the courts that compensation payments should be limited to two years instead of five.

Strathclyde has instructed headteachers since last April not to run departments where there is no appointed principal teacher. Jim McNair, secretary of the Headteachers’ Association of Scotland, described the situation as “messy waters”.

Mr McNair commented: “Headteachers have been put very much on their own by the authority and where they have asked for clarification, they have not had it.” The association is concerned that assistant principal teacher posts are now being phased out.

Ms Marsh accepted that the judgments “drive a coach and horses” through the Scottish Joint Negotiating Committee’s agreements. “This would have to spell the demise of the SJNC,” she said.

Another case involving 168 special education instructors could cost the region and its successor councils Pounds 5 million. Seventy-nine heads of nursery centres and pre-five centres also say they are doing the work of nursery headteachers and should be paid as such.