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

"Over the next three years the bureau's [funding] will fall by approximately 10 per cent," Chief statistician David Kalisch said.

"In line with this decline in funding, average staffing levels will need to decline by around 17 per cent over the next two years."

Such a reduction would take one-in-six or 480 full-time equivalent jobs out of the bureau's 2833 positions.

Up to 100 staff were given voluntary redundancies in March, following a further 120 staff members who were axed late last year.

The bureau is to appear before a Senate estimates committee on Wednesday where it will face questioning over the roll out of the $122 million same-sex marriage survey and the census.

Labor's shadow assistant treasurer Andrew Leigh said the bureau was struggling under the additional workload due to "an unnecessary opinion poll on marriage equality".

"[Prime Minister] Malcolm Turnbull now needs to confirm whether more than 480 positions are set to be axed over the next two years as the bureau struggles with the Liberals' ongoing campaign to weaken the public service," he said.

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 will deliver the next census.

Mr Kalisch said there was also a high demand for statistics in a number of other areas, such as time use and mental health, that the bureau is not able to undertake with existing resources.

The bureau has suggested reductions to surveys on car sales, household use of information technology, housing and lending finance and tourism maps from next year to avoid compromising core economic statistics.