The ACT Public Service would need to hire about 150 more Aboriginal and Torres Strait Islander staff over the next 18 months to meet an ambitious employment target.

The bureaucracy is struggling to implement plans to boost the indigenous composition of its workforce to at least 2 per cent by 2015-16.

Concerns have also been raised about the proportion of the ACT government's Aboriginal and Torres Strait Islander public servants who are employed in lower-level or non-continuing positions.

About 258, 0.9 per cent, of the territory government's public servants, are believed to be Aborigines or Torres Strait Islanders.

A Legislative Assembly committee, chaired by former indigenous affairs minister Chris Bourke, pictured, will begin public hearings on Wednesday into the progress of the indigenous employment strategy.

Public service chiefs have told the inquiry that the number of staff who identify as indigenous has risen from just 176 in 2010.

''The number of Aboriginal and Torres Strait Islander employees has progressively increased since the implementation of the employment strategy,'' the public service submission to the inquiry said. ''While this is a pleasing result, higher numbers at this stage of the strategy were anticipated, with the shortfall at around 0.2 to 0.3 per cent.''

The ACT's Aboriginal and Torres Strait Islander Elected Body has expressed concerns that one-third of the Aborigines and Torres Strait Islanders employed by the territory

were on temporary contracts. Elected Body chairman Rod Little was also worried about a lack of sustainable career paths for people who entered the local public service through an indigenous traineeship program.

''The Elected Body has also noted … that many of these former trainees are 'trapped' in the lower levels of the public service,'' Mr Little submitted to the inquiry.

''We are deeply concerned at the lack of aspirational career paths and development position levels these mostly young people were recruited to.''

Only 0.4 per cent of senior officer-level positions were filled by Aboriginal and Torres Strait Island people.

Despite his concerns, Mr Little praised the ACT government for having an Aboriginal and Torres Strait Islander employment strategy.

The proportion of staff in the Australian public service who are indigenous fell from 2.8 per cent to 2.3 per cent between 2002 and June this year.

In 2009 the federal government made a commitment to increase indigenous employment in the federal public sector to 2.7 per cent by 2015.

Indigenous members of the ACT Public Service earn, on average, about $10,000 less than their non-indigenous colleagues.