"As soon as the information is available,we will advise affected staff members of any underpayments and rectify the error as soon as possible,"he said."I genuinely regret that errors have occurred in the payment of employee entitlements and want to assure you that any errors were completely unintentional."

The Sydney University branch president of the National Tertiary Education Union,Kurt Iveson,said staff wanted to know how the error occurred.

"They were very explicit today that they didn’t know how big it is,or how many people were affected,"he said.

Dr Iveson said the casual workforce had been decimated due to austerity measures."Now we find out everything we’ve saved it is going to be spent fixing a screw-up that’s been going on for years,"he said."It’s infuriating."

The union's president Alison Barnes called for tougher penalties for wage theft."But we also need to end the mass casualisation of university staff,which creates the conditions for wage theft in the first place,"she said.

Unlike theUniversity of NSW,which has begun a redundancy process,and theUniversity of Technology Sydney,which last week detailed its bleak outlook for next year,the University of Sydney has not released forecasts for 2021.

But in an email to staff earlier this week,Dr Spence said international enrolments were unlikely to bounce back before the beginning of the next academic year,as the university had hoped,so the revenue forecasts for next year would be revised downwards.

"We are gathering as much information as possible for our scenario planning and exploring options on ways to address the expected revenue shortfall for next year,"he wrote.

"It is important that we are as confident as we can be before making any further decisions,with a focus on preserving our education and research excellence and ensuring the future viable operation of the University."