More than 70 jobs are expected to be lost at Preston’s prison in a bid to cut costs.
Under a draft report, 71 jobs could be lost overall, with 62 of the losses coming from uniform staff.
Union leaders have raised fears cuts could mean the safety of staff, prisoners, and the public would be put at risk.
Job cuts at HMP Wymott in Leyland are also expected, although a report has not yet been finalised.
Steve Baines, North West representative for the National Executive Committee of the Prison Officers Association (POA), said: “This is a national process and the POA have agreed to engage and see where we end up.
“It is a draft report at this stage so we have got an opportunity to go to them and dispute these figures and get more details on what it is they are looking at.
“They are looking at losing 62 uniform posts and 71 staff in total at Preston.
“We are working through the process but we won’t sell the health and safety of our members. If it isn’t safe, we won’t agree to it.
“We will work with management to come up with safe proposals.”
HMP Preston is one of 60 jails nationally being looked at in the first phase of a two-year plan to cut costs. A demonstration was held outside the prison yesterday.
Michael Spurr, chief executive officer of the National Offender Management Service (NOMS), said: “We will never do anything to compromise the security and safety of prisons, but we are committed to reducing costs for the taxpayer.
“Where this means reducing staff numbers, we will work constructively with trade unions to do everything possible to avoid compulsory redundancies.”