O'Farrell not worried about prison numbers

NSW Premier Barry O'Farrell has no concerns prison officers won't be able to cope with any increase in prison numbers in the light of new mandatory sentencing laws.

The Public Service Association of NSW (PSA) claims the new mandatory minimum sentences will increase inmate numbers and put further pressure on prison staff.

But Mr O'Farrell says the prison population often goes "up and down".

"I am amazed at the PSA suggesting that prison officers can't cope with looking after prisoners - they have done it with great skill for many years," he told reporters.

"So I have no concerns about that."

He is confident the government can deal with the consequences of the tough new laws.

The reforms include a mandatory eight-year sentence for fatal one-punch assaults where alcohol or drugs are involved.

PSA General Secretary Anne Gardiner she says the prison officer to inmate ratio is already at dangerously low levels.

"Unless this government is prepared to address these staffing ratios and the working conditions of prison staff, including the restoration of proper workers' compensation provisions, any increase in inmate numbers is unacceptable," she said.