Two lecturers' unions, the AUT and Natfhe, are boycotting all exam-marking and coursework assessment - and in the AUT's case exam-setting - until they see a "substantial" pay rise for members.
With graduations threatened, universities such as Cambridge and Keele have already set in motion "emergency measures" - such as using exam papers from other sources - the AUT said.
"I continue to hear from more students' unions who want to join forces to reiterate our full support for the industrial action taken by the AUT at the moment, " said Ms Stark - who is also the NUS national women's officer-elect.