The union representing hundreds of technical workers in the defence establishment says the cuts to science and engineering will eventually cost lives on the battlefield and leave Australia a weaker military nation.

Hundreds of Defence scientists and engineers have backed the appeal to the Prime Minister to ease off on the cuts.

Professionals Australia says about 100 of Australia's top military scientists and engineers have left the Defence Department, the Defence Science and Technology Organisation and the Defence Materiel Organisation in the past year through redundancies and natural attrition.

The jobs cull is expected to cut, from six scientists to two, the DSTO's technical team for the $24 billion Joint Strike Fighter - the nation's largest ever defence purchases.

And the Australian Maritime Warfare Centre, based at Sydney's Garden Island, is slashing a third of its civilian staff.

With another 150 jobs expected to go in the next 12 month, Professionals Australia chief executive Chris Walton said hundreds of Defence scientists and engineers had asked him to plead their case to the top of government.

''We have seen an overwhelming commitment and belief from members across Defence and, more broadly, about the importance of engineering and science to the integrity of the Defence mission,'' he said.

Mr Walton said he wanted to meet with Mr Abbott and warned the government should not fall into the ''penny wise pound stupid trap'', of cutting the capacity to deliver value for money in weapons development and purchases .

''Our great concern is that cuts to science and engineering jobs and conditions will expose Defence personnel to unnecessary risk and undermine national security,'' he said.

"On the behalf of members, we called on the Prime Minister to act in the national interest and take action to call a halt to proposed cuts to Defence science and engineering and instead properly address resource gaps and in-house capability.

''We have asked to meet with the Prime Minister to discuss how we can meet these critical challenges together. We await his response."

The union is also trying to bring the Defence Department to the negotiating table for talks on a new enterprise agreement after the deal covering the department's 23,000 public servants expired on Monday.

With a ban on back-pay for new public service wage deals imposed by the Abbott government, Mr Walton said his members were anxious to get the talks under way.

''The road to productivity is not paved by goading your workforce and treating working people with a lack of respect and decency,'' he said.