The delay comes after six months of negotiations and despite CSIRO chief executive Dr Larry Marshall telling a senate estimates hearing the deal was "very close" to completion in early June.

But on Wednesday, a National ICT Australia (NICTA) spokeswoman said the merger was still being discussed and no final decision had been made regarding staffing.

"The proposed merger is an important milestone for digital technology research in Australia and we are fully committed to investing the necessary time and resources to ensure a smooth transition," she said.

NICTA's current funding will expire in June next year leaving close to 600 students and staff without funding in the absence of a merger with the CSIRO.

Dr Marshall said the merger, which will see the peak science body's production team merge with NICTA, could see 200 support staff lose their jobs.

He said senior staff had been consulted about the potential staffing modelling with all staff to be consulted once the merger was formally approved.

But on Wednesday, a CSIRO Staff Association spokesman said the workforce was still apprehensive given the lack of a final decision.

"[There is] no new information on potential staffing impacts but I think it's fair to say the lack of information and staff consultation is a concern," he said.

Shortly after Dr Marshall's appearance at estimates, CSIRO Staff Association secretary Sam Popovski said there should be no job cuts or involuntary redundancies as a result of the merger.

"Only last November we saw the loss of 25 full time equivalent positions … resulting from the federal government's deep cuts to CSIRO funding," he said.

"The government is seeking the merger so it should be fully funded in order to retain NICTA staffing levels going into CSIRO."

In February, Mr Popovski wrote to Dr Marshall to say staff were "extremely concerned about the lack of updated information being provided to them and the potential implications of any merged or new entity involving CSIRO and NICTA staff."

Dr Marshall told the senate hearing it was inevitable that some staff working in support roles would lose their job as a result of the merger.

"We are working with the NICTA team to establish where the areas of overlap are and as you may imagine, there are a lot of areas of overlap in the support functions so HR, finance, marketing and so on."

"If the merger goes ahead then obviously there will be way, way fewer job losses than if it doesn't, because the company will run out of money in the middle of next year."

Under the current merger proposal, a separate company would be established with a chief executive and a board although it would remain part of the CSIRO for a term.

"We continue to work on projects with impact for Australia while also working with each other and our stakeholders to bring about this important merger and preserve this capacity in Australia," said the NICTA spokeswoman.