The figures suggest the local government area will hold 46,500 people in 17 years' time, an extra 6250 people than in 2011.

The modest growth predicted is at odds with research conducted by eminent demographer Bernard Salt, commissioned by Dubbo City Council in 2012 at a cost of $50,000.

He and his KPMG team had projected Dubbo's population would hit the 51,600 mark within 25 years.

Yesterday Dubbo mayor Mathew Dickerson called the department's latest projections "disappointing" and anticipated further discussions with its number crunchers.

Dubbo's growth is forecast by the department to crawl along at an average rate of 0.7 per cent per year until 2031.

It identified a growing young population and increase in rate of births as the main driver of population change.

By 2031 the number of households would increase to 19,100, up by 3400 from 2011 Census of Population and Housing data, but their make-up was forecast to contract.

The department projected average household size would fall to 2.36 people in 2031 from 2.51 people recorded in 2011.

The 2014 edition of the NSW population projections took into account the 2011 census, final recast estimates by the Australian Bureau of Statistics for the period 1991 to 2011, and the latest data and expertise on fertility, mortality and migration.

Cr Dickerson questioned if the department had considered all relevant factors and if droughts in the past decade were still shaping its projections.

Dubbo had land available and its local environmental plan, and was more affordable compared with Sydney, he said.

Last week's announcement of preparation to build the National Broadband Network (NBN) to an established area of Dubbo ahead of many other regional centres was another factor to consider, he said.

The council was "planning for a city of 55,000 people by about 2036" and the mayor warned that the department's projections could become "a self-fulfilling prophecy" if the state government used them to justify not planning more schools, police and other services.

"It's disappointing to see they haven't taken notice of the data we spent at a lot of time and effort on," Cr Dickerson said.

"They've just gone ahead with the way they've done it in the past."

He stood by the projections of KPMG, saying that although the council paid for the research, the firm staked its reputation on delivering realistic data.

He foreshadowed further discussions with the department, including a request for it to review the KPMG projections.