The Department of Education, Employment and Workplace Relations' internet vacancy index declined to a seasonally adjusted 64.9 points in the month, to be 24.8 percent lower than a year ago.
In trend terms, internet job ads are at their lowest since the series began in January 2006.
Demand for professional workers dropped by 5 percent in the month, and there was a 4.2 percent decline in vacancies for clerical and administrative workers.
For IT workers, vacancies for IT professionals were down by 3.4 percent for the month, giving a yearly change of -27.3 percent. The reading was even worse for the engineering, IT, and science technicians category, which was down by 5.7 percent for December, and gave a yearly change of -40.7 percent.
However, vacancies increased in four of the eight occupational groups monitored by the department.
The strongest monthly increase was for machinery operators and drivers, rising by 4.6 percent, followed by a 2.2 percent rise in community and personal service workers.
Only Tasmania and the Northern Territory posted a rise in jobs ads in December, increasing by 1.8 percent and 0.5 percent, respectively.
The biggest fall was in Victoria, a drop of 3 percent in the month, followed by Queensland with a 2.6 percent drop, and Western Australia recorded a 2.5 percent fall.
Jobs ads declined in all states and territories over the year, led by a 32.2 percent fall in Queensland, and a 29.9 percent fall in Western Australia. All other states recorded falls of between 29 percent to 15 percent.