As it shrinks by at least 400 public servants before July 2019, the agency has admitted it won't find all of its cuts through staff attrition alone and will have to let go of office-based staff through redundancies.

The ABS's attrition rate, excluding redundancies, was about 7 per cent last year and the bureau has told senators it won't renew unneeded temporary jobs.

Public servants exiting the 2800-strong agency will have their jobs automated, and other departing staff include administrative workers and those whose work has been centralised in its National Data Acquisition Centre in Geelong.

The bureau said in a response to a Senate estimates question on notice it will target office-based public servants, leaving its 400 interviewers collecting data from homes for surveys unscathed by cuts.

The fresh round of job losses will hit the ABS following a 120-staff cut in 2016 and 100 redundancies the following year amid budget cuts.

Labor MP for Fenner Andrew Leigh said the Coalition had undercut and undermined the ABS since 2013.

"Important surveys have been axed. Major IT failures have wasted the time of respondents, and lowered the quality of data," he said.

"Savage cuts to the Australian Bureau of Statistics are a false economy.

"If the Turnbull government cared about evidence-based policymaking, it would be properly staffing the Australian Bureau of Statistics."

The main public sector union said cuts to the ABS had stopped it collecting statistics, and that losing another 400 jobs would be catastrophic for the agency and those relying on its data.

Community and Public Sector Union acting national secretary Michael Tull said 160 people had been sacked at the bureau in the last 14 months.

"This should be a scandal - ABS data is essential to nearly every major policy issue and decision the nation has to make, and to deny ourselves access to that data and thereby reduce the quality of decision making is a classic case of false economy. It has to stop," he said.

As the government announced last year the ABS' workforce would shrink by 17 per cent, Australia's chief statistician David Kalisch warned it did not have the resources to undertake all the activities government agencies demanded.

Data used to assess housing affordability could be among a swag of surveys on the chopping block as the bureau looks to find millions of dollars in savings in its budget, along with figures on agricultural land ownership, industrial disputes and internet activity.

The bureau receives $290 million a year in funding, but is set to face a cut of up to $29 million a year once a business transformation program is completed in 2020, a year before it conducts the next census.