Two-thirds of recently qualified second-level teachers are in precarious employment, according to a survey commissioned by the Association of Secondary Teachers in Ireland.
The Red Sea survey is based on responses from 775 ASTI members and is published ahead of the union's annual convention, which takes place in Killarney next week.
It found that 66% of teachers employed since 2010 were on temporary or part-time contracts.
Almost one in five said they were supplementing their teaching income by working a second job.
Commenting on the findings, ASTI President Ed Byrne said a lack of job security, coupled with differential pay scales for teachers employed since 2010, represented a critical threat to the future of second-level teaching and education here.