Security firm G4S said around 123 full-time positions were at risk at the prison, mostly in management, operational support, facilities management and administration areas, ahead of its transfer to the private sector in October.
The new staffing levels “will be more in line with the levels G4S has successfully and safely adopted in the four other prisons it currently operates in England and Wales”, a company spokeswoman said.
Jerry Petherick, managing director of G4S Offender Management, said: “When the Government decided to move operational control of HMP Birmingham to us, it was in the knowledge that efficiencies needed to be made.
“We have been transparent with staff from the very beginning, making it clear that in order to deliver the savings required by Government, some job losses were sadly inevitable.”
He said the announcement would be welcomed by staff by providing more certainty about how they will be affected.
He said he planned to make HMP Birmingham one of the flagship prisons in the UK.