The jobs of about 20 per cent of the Commonwealth science group's 6500 staff were plunged into uncertainty last week after Public Service Minister Eric Abetz imposed a hiring ban on the federal bureaucracy.

The staff freeze threatens to paralyse some of the organisation's premier research projects, with a ban on hiring, extending or renewing contracts effective immediately. Fairfax Media understands the only exceptions are post-doctoral positions and indigenous recruitment.

''It's going to be a huge problem,'' said one staff member, who wanted to remain anonymous.

CSIRO's executive and senior staff have been frantically seeking explanations from government as to how the edict is to be interpreted.

''Are there any loopholes or special cases? We're trying to figure it out. The meetings are ongoing,'' the staff member said.

It is not clear if the bans apply retrospectively to the series of three, four and five-year Australian Research Council fellowship positions - grants which Education Minister Christopher Pyne will announce on Friday.

''We have an agreement with the ARC, so does that mean they are exempt? We don't know. It's a complete mess,'' another CSIRO employee said.

After Thursday afternoon's talks between the CSIRO Staff Association there appeared to be a large gulf between the sides, with the association saying little and management accusing it of exaggerating the number of jobs on the line.

After the minister's announcement last week, CSIRO chief Megan Clark said the group, which has a much higher proportion of ''term'' staff than other public sector operations, would not be ''entering into any new, or extending existing term or contract employment arrangements''.

The CSIRO has about 990 ''term'' workers and about 440 casual staff.

As confusion continued over the jobs of thousands of temps, contractors and other ''non-ongoing'' public service workers in government departments around Australia, the service's workplace authority, the Public Service Commission, had still not responded to departmental bosses' pleas for guidance on the new rules.

''Further instructions to agencies and APS employees on the interim recruitment arrangements should be available shortly,'' a commission spokeswoman said.

CSIRO Staff Association president Michael Borgas said he and his colleagues were meeting the group's human resources boss Trevor Heldt to try to get some answers on the fate of the term workers.

''It's a massive concern,'' Mr Borgas said.

But after Thursday's meeting, a CSIRO Staff Association spokesman said they were waiting for more information from management before making any further comment.

A CSIRO spokesman was likewise saying little about the talks but said the number of jobs under threat had been exaggerated.

''The figure quoted of 1500 potential staff under uncertainty is a significant exaggeration,'' he said.

''There are approximately 300 non-casual term staff whose terms finish in the 2013-14 financial year and a similar number in the period 2014-15. It is noteworthy that, in normal circumstances, a proportion of these terms are not renewed in any given year.

''Also a significant proportion, up to 40 per cent in some years, of our term appointments are for the purposes of employment of post-doctoral fellows and similar transitional science roles which in the normal course of events do not come with an expectation of renewal,'' the spokesman said.

He said that about half of CSIRO's casual staff came in for renewal each financial year.

''In terms of casual staff the numbers of projected term completions are in the range of 150 to 250 each financial year,'' he said.

''CSIRO uses casual staff primarily for seasonal work or for covering absences of administrative support staff - which provides employment opportunities for people who prefer this mode of employment or who may not be able to commit to full-time employment.''

Younger CSIRO staff and research scientists head-hunted from overseas are massively over-represented in the ranks of term workers at the group and the proportion of non-ongoing staff to permanent employees has been an industrial relations battleground at the organisation for several years.