The Defence white paper, released on Thursday, announced the creation of 800 new roles in intelligence, space and cyber security divisions. Another 400 roles will be created in strategic policy, engineering, IT and diplomacy.

But the government has capped the number of public servants within the Department of Defence at 18,200, prompting unions to fear close to 1000 staff will be made redundant given current staffing of around 18,000.

According to the white paper, the new roles will be accommodated by ongoing cuts to the bureaucracy and existing staff will be retrained to perform specialist functions.

But Professionals Australia official Dave Smith, whose union represents technical staff employed by the government, said the majority of new roles would require specialist knowledge unlikely to be found in the existing workforce.

"Defence has identified the need for 1200 new roles but they have to do it within the envelope of 18,200 APS employees," he said. "A 1000 will have to go. It's that simple."

"These are not positions that you could retrain for without extensive background in relevant technologies."

The Department of Defence has shed close to 20 per cent of its workforce since 2012 when 22,230 public servants were employed by the government.

More than 4000 staff have left the department in recent years with management accepting the voluntary redundancies of an additional 565 executive level staff in November.

Mr Smith said the proposed restructure would only add to a loss of expertise and experience.

"We have no confidence that these additional roles will halt the erosion of critical science, engineering and technical roles despite more than $50 billion being put into purchasing and maintaining new capability in the submarine space alone," Mr Smith said.

According to the white paper, maintaining the capability of public servants is "one of the most challenging jobs" facing the department in coming decades.

"To meet these demands, the government will undertake the largest single rebalance of the integrated Defence workforce in a generation through the implementation of the First Principles Review," the white paper said.

"All parts of the Defence workforce will need to upgrade their skills as part of building a more capable, agile and potent future force."

The white paper also announced intentions to send more civilian staff overseas on diplomatic missions, with tertiary training provided to those who need it.

"Defence will increase the number of personnel with intermediate and advanced language skills to support our enhanced international engagement, with a focus on languages in the Indo-Pacific region," the report said.

The workforce restructure was announced on the same day the department opened voting on a revised pay deal, which offered a 2 per cent increase each year for three years.

The government continues to prioritise efforts to "increase the leadership capabilities of executive level staff" with new graduates to be subjected a greater policy focus. Graduate numbers increased by 55 per cent this year from 161 positions in 2015, to 250.

Shadow Defence spokeswoman and Canberra MP Gai Brodtmann said the white paper revealed more public servants were likely to lose their jobs.

"The government's own First Principles Review said that Defence has already had to replace sacked public servants with military personnel to ensure functions continue," she said.

"This cycle of shifting positions from ADF to civilian to contractor has to end. It is disruptive and costly."

The government acknowledged the need to embrace a more diverse and inclusive culture as part of the restructure. Women account for 41 per cent of department staff but only 15 per cent of the ADF workforce.

"Gender equality and increasing female participation in the Defence workforce and in senior leadership roles is fundamental to achieving Defence capability now and into the future," the paper said.

The government also announced intentions to grow the permanent ADF workforce to around 62,400 by 2026, which would take it to the largest number since 1993.