The number of doctors in the ACT is falling as Canberra continues to report the lowest rate of bulk-billing in the country.

The ACT was the only state or territory to report a decline in the number of working doctors between 2008 and 2012, according to a report issued by the Australian Institute of Health and Welfare.

The Medical Workforce 2012 report showed an increase in the number of full-time-equivalent doctors across all states and territories except the ACT, which recorded a decline from 488.2 to 456.3 full-time-equivalent medical practitioners per 100,000 people.

The new figures, which outline an ageing workforce older than the national average, coincide with government statistics showing that the capital's rate of bulk-billing is lagging at almost 30 per cent lower than the national average.

ACT Chief Minister Katy Gallagher declined to comment on the report.

ACT Health director-general Peggy Brown said the fall in the rate of doctors per population in the ACT may be due to registration changes.

Dr Brown said the introduction of national registration in 2010 meant doctors practicing in both the ACT and NSW could register in one state to work across jurisdictions, which could explain a drop for ACT-based registrations.

''We don't believe that the number of actual practitioners in the ACT has dropped,'' she said.

Dr Brown also acknowledged the ageing medical workforce within the capital, which increased from an average age of 44.2 years in 2008 to 46.1 years in 2012.

The percentage of working doctors aged over 55 years also increased from 20.7 per cent to 26 per cent over the four-year period.

Dr Brown said the government had been focusing on increasing junior doctor numbers to tackle impending retirements and the trend towards greater work/life balance, with employment figures rising from approximately 50 in 2007 to 96 in 2014.

''The bulk of those came from ANU, so they're home-grown,'' she said.

Australian Medical Association ACT branch president Andrew Miller described the supply of qualified practitioners in the capital as patchy, but said the shortage of GPs was ''not as real'' as Canberrans believed.

Dr Miller said there were concerns in the medical community over a lack of positions for interns and junior doctors and called on both the ACT and federal governments to provide further funding.

''We have to have vocational training positions here and that's going to involve some expense,'' he said. ''… There's going to have to be more money.''

Nationwide, the number of medical practitioners rose by more than 16 per cent over the four years to 2012, bringing the total registered number to 91,504.

The report follows statistics issued by the federal Health Department which show that the ACT has the lowest rate of bulk-billing in the country.

A total of 51.3 per cent of GPs bulk-billed in the ACT in the September quarter of 2012, compared to 86.5 per cent in NSW and a rate of 81.6 per cent nationally.

It represents a slight increase from the same period in 2008, when the rate was 49 per cent and an even greater improvement from the low of 43.3 per cent in the December quarter of 2010.

The total Medicare bulk-billing rate was also recorded as lower than the rest of the country at 64.9 per cent as of the September quarter in 2012.

The national rate was recorded at 76.8 per cent for the quarter, while the rate for the Northern Territory was listed at 84.7 per cent.