At Birmingham, 70% of teaching staff are on insecure contracts, while at Warwick it is 68%.
This is because, despite rising employment, the UK leaves many grads on insecure contracts or underemployed.
Academics on insecure contracts form "a reserve army of precarious and exploited labour", claimed Sally Hunt, general secretary of the UCU.
UCU believes a critical weakness of our current system is the precarious employment of university teachers, 49% of whom are on insecure contracts".
"While institutions are closing, privatising services or charging for access, the staff who guard our nation's cultural treasures are languishing on low pay and insecure contracts".
Some of the staff involved, whose claims were gathered in partnership with workers rights group Pay Justice, have worked for the company for considerably longer, despite being employed on insecure contracts.
According to analysis of the official figures by the University and College Union, more than half of academics in Britain's universities, where students are paying £9,000 a year in fees, are employed on temporary or insecure contracts.
Jonathan White, a spokesman for the University and College Union (UCU), which is holding a national day of action on Thursday to highlight the problem, says it's a "scandal" that insecure contracts have proliferated.
Wedell says the financial and psychological strain has got to many, as the US higher education (HE) jobs market has shifted from full-time, tenured posts towards insecure contracted work.
