Secondary school teachers have rejected a 5% pay offer, with 70% saying they would back strike action without an improved deal.
The Scottish Secondary Teachers’ Association (SSTA) said 80% of its members turned down the proposal put forward by local authority body Cosla.
The negotiations come in the midst of a cost-of-living crisis caused by rising inflation and soaring energy prices.
BBC Scotland has approached Cosla for comment.
Cosla has also been locked in industrial disputes with education staff and cleansing workers in recent months.
Seamus Searson, general secretary of the union, said: “SSTA members have given everything in the last number of years to keep education going and to ensure that all young people did not lose out during these difficult times.
“Teachers are walking away from the job because of the excessive workload and a poor pay offer only adds insult to injury.”
The dispute between council staff and Cosla was resolved earlier this month after the intervention of First Minister Nicola Sturgeon, with unions praising her role in bringing negotiations to an end.
Mr Searson added: “The Scottish government must step up to the plate and be prepared to put in place a pay offer that will retain teachers and recognise their tremendous efforts over the last few years.
“Teachers are already struggling to keep schools running with morale very low and Cosla’s disparaging pay offer only adds to their feeling of being grossly undervalued.”