Sydney prison officers on two-day strike

Officers at the jail suffered the highest number of serious assaults in the state, and the number of assaults among inmates was the second highest in the last financial year, PSA assistant general secretary Troy Wright said.

In that same period, an inmate is believed to have set fire to the prison, causing some $8 million in damage.

"Only in the last few weeks a prison officer was king hit from behind. Officers have had shivs (handmade weapon) held to their throats and others have been punched in the face," Mr Wright said.

"It's easy to see something is going seriously wrong," Mr Wright said.

Staff are also routinely asked to pick up extra work at the chronically understaffed jail, with weekends being the worst affected.

"Understaffing is chronic and causing a lot of these problems. We know this jail is short staffed everyday," Mr Wright added.

"The longer inmates spend locked in their cells, the more agitated they get and the more likely they are to assault staff, or start riots or fires."

Prison officers are in the midst of negotiating a new enterprise agreement with their employers, MTC Australia, and are seeking a 3.5 per cent wage increase.

They claim to be stuck on an offer from their employer of 2.5 per cent.

Prison officers also want to see staffing levels increase and decrease the demand to work on weekends.

"MTC Australia has a contingency plan in place to ensure the prison can continue to operate safely and securely with an appropriate number of staff and with minimal impact," the company told AAP.

"We have been negotiating with the union in good faith since May this year and we will continue to work with them to reach an agreement.

"MTC Australia has offered custodial staff a 12 per cent pay rise over four years."

AAP reached out to Corrections Minister Geoff Lee, who declined to comment on the industrial action.