While the overall number of public servants has dropped in the past year, the number of people with disabilities in the public service has fallen almost continually since 2007.

In 1994, the Australian Public Service employed 8063 people with disabilities. In 2013, just 4450 - the lowest number in at least 20 years.

Public servants with a disability were also substantially more likely to resign and less likely to retire than other workers.

The figures came one year after APS Commissioner Stephen Sedgwick launched the disability employment strategy As One to increase the number of people with disabilities in the public service. But the new statistics showed the strategy had not yet succeeded.

Mr Sedgwick this month said not enough progress had been made in bringing people with a disability into the public service.

''It remains a serious concern that the representation rate is not rising of those who identify as indigenous or as having a disability,'' he said.

''We need to be vigilant - especially vigilant - to be sure we maintain the diversity of our workforce as we downsize in the years ahead.''

The latest State of the Service report showed that although engagements of people with disabilities rose sharply in 2012-13 to 2.1 per cent, that figure still dwarfed the number of separations, which at 5.1 per cent was a seven-year high. Both of these numbers were a proportion of the overall engagements and separations in the public service.

Australian Disability Discrimination Commissioner Graeme Innes said the public service's record for employing people with disabilities was shameful.

''This just reinforces my serious concerns about this issue. The public service can't tell private employers to employ people with a disability when it's got such an appalling record itself,'' he said.

Only this week, a blind public servant spoke out about her expectation of losing her job with the Office of Parliamentary Counsel after a ''spill and fill'' process to reduce staff numbers.

Amanda Heal told Fairfax Media she wanted answers as to why she and two colleagues - one of whom is pregnant, the other impaired by workplace injury - were the ones told they were ''potentially excess''.

Mr Innes called for significant changes to the public service, which he said until now had just been playing around the edges of the problem.

Enforceable targets tied directly to the pay bonuses of department secretaries were among the measures he believed necessary.

''There's no significant commitment towards changing the situation, and without that at senior levels, it's just not going to happen,'' he said.

The president of People with Disability Australia, Craig Wallace, was a member of the public service for 15 years, during which time he said it was sometimes difficult to get even the most basic accommodations.

He said the new numbers did not surprise him at all.

''I really think the public service needs to take a long hard look at what its policies and practices are supporting, and at keeping people with a disability in the public service,'' Mr Wallace said.

He added that from his experience in the service, public servants were more likely to be urged to resign than retrenched or terminated.

Of all the people with disabilities who left the public service in 2012-13, 64 per cent resigned, compared with 46 per cent of all other public servants.

''What they will normally try to do is ease people on a resignation pathway. People [with a disability] end up in performance management,'' Mr Wallace said. ''What the separations would be code for is people who aren't being supported.''

All figures mentioning people with disabilities in the report are people who have identified themselves as having a disability, which may include mental illness and work-related acquired disabilities.