On Wednesday last week, a number of staff were told their jobs would not exist on Monday. The announcement was made as the NGA scramble to find savings imposed by the federal government's efficiency dividend.

Unions and gallery sources have confirmed the head librarian job will no longer exist with other senior positions cut.

NGA acting director Kirsten Paisley would not confirm the individuals approached but said they would continue to be employed while redeployment was considered.

"Seven permanent positions have been affected in the restructure," she said. "We anticipate the remainder of the 15-20 positions will be obtained through natural attrition or contracts not being renewed."

Letters seen by Fairfax Media show staff were told they would be considered for vacant positions without competition from other applicants, provided they "possess the ability to perform the tasks of the position within a reasonable period".

Community and Public Sector Union deputy secretary Beth Vincent-Pietsch said the cuts included senior staff. She has urged the NGA to consider voluntary redundancies across the entire workforce.

"We were told that three of the positions were SES officers, seven were permanent staff and the rest were contractors whose employment would not be renewed," she said.

"We have real concerns about how this will impact workloads but also the way these cuts were handled. Staff given letters without any real notice."

Ms Vincent-Pietsch said she sympathised with NGA management and hoped most of the jobs could be saved.

"We know they are caught between a rock and a hard place and are making these terrible decisions because they have no other choice, not because they are ideologues," she said.

The job losses were outlined in the 2016-17 federal budget, which announced that 63 full-time positions would be cut from cultural institutions over 12 months.

The gallery was also hit by the mid-year economic and fiscal outlook, which took $36.8 million from "cultural and collecting entities within the arts portfolio"

Meredith Hinchliffe, a long term NGA volunteer and donor, said staff were frustrated by cuts but many felt the announcement had been badly handled.

"It concerns me as a donor and a volunteer that two senior people are leaving and that the gallery will be losing their scholarships and the international reputations they bring," she said.

"[The library] is recognised all around the country as the leading art library and to lose the head librarian - who is a big figure in the international scene - is a possible threat to the library."

Some staff have also questioned the timing of director Gerard Vaughan's overseas trip last week.

Ms Paisley said Mr Vaughan had outlined a restructure on September 8 and travelled to finalise the loan of Jackson Pollock's Blue Poles painting to the Royal Academy of Art in London.

A petition opposing the cuts and describing them as "philistinism", prepared by Canberra MP Andrew Leigh, has received close to 500 signatures since launching on the weekend.

"This year the Turnbull government has ripped an extra $36.8 million out of Australia's cultural and collecting institutions while at the same time planning to throw away $175 million on a divisive and pointless plebiscite about marriage equality," Mr Leigh said.