Earlier this week the Appeal Court over-ruled awards made to two teachers and a factory worker.
A fourth award to a training centre employee was upheld because she had complained about her intolerable workload.
NUT general secretary Doug McAvoy said he was disappointed that rulings in favour of teachers Leon Barber and Penelope Hatton who both retired on ground of ill-health in 1996, had been reversed.
French teacher Mrs Hatton was awarded pound;90,765 damages at Liverpool County Court after suing St Thomas Becket RC high school. Mr Barber, a head of mathematics, sued Somerset County Council and won pound;101,041. The rulings were both overturned on Tuesday.
Mrs Hatton intends to challenge the decision in the House of Lords. She refused to comment on the court's decision. Mr Barber was unavailable for comment.
Mr McAvoy said "We shall continue to pursue legal claims on behalf of members whose cases fit the tests the Court has laid down."
Implications for schools - see next week's Briefing section.