More than 250 public servants from federal Environment Department will be out of a job by Christmas as the department tries to cut its budget by more than 20 per cent.

Staff were told on Monday that the layoffs would see another 230 jobs slashed in the next three years, on top of 190 bureaucrats who have already taken redundancies from the cash-strapped department, a total reduction of 670 workers.

And there could be worse to come with departmental bosses warning frankly that the government’s Commission of Audit could inflict even more pain.

The Canberra Times revealed last month that the department’s budget would be deeply slashed over the next four years with most of the cuts coming in staffing numbers, a move that could reduce departmental numbers to fewer than 1700 - from 2300 last year - in coming years.

The reality of the cuts was brought home on Monday afternoon with employees told by their bosses that a new voluntary redundancy round will begins next week, open to all departmental staffers.

The cuts are also expected to bite into the Environment’s top brass with senior executive ranks to be reduced by 25 per cent – which is understood to equate to about 20 jobs.

The department’s long-awaited strategic review reveals a dire budget position with a reduction of $100 million needed in the next four years from $460 million in 2013-14 to $361 million 2017-2018.

The job cuts are expected to target junior and middle management at EL1 and two level.

Public sector unit the CPSU said it was dismayed by the continued cuts.

“This Government has dealt yet another blow to Australian public services,” the union’s national secretary said.

“The Government is cutting another 480 jobs over the next three years, and the Department admits there may well be even more after the National Commission of Audit comes out.”