The jail staff's union says ACT officials are ''scratching around like chickens'' after realising they can't overcome guards' opposition to the scheme.

The government had originally hoped its needle and syringe program, designed to prevent the spread of blood-borne diseases within the prison, would begin last year.

But the plan has been bogged down since its original announcement in August 2012, following strident opposition from guards' and nurses' unions.

The delays have frustrated public health advocates who had praised the government's stance, saying there was compelling evidence it would help control diseases like hepatitis C.

But the Community and Public Sector Union, which represents guards, said there had been almost no change to the proposal in the past 16 months, and certainly nothing to overcome their ''insurmountable'' opposition to allowing needles into the Alexander Maconochie Centre.

The union's support is critical because a clause in the guards' workplace agreement prevents any needle exchange from going ahead ''without prior consultation and agreement'' from unions.

Chief Minister Katy Gallagher said the government was still committed to the program, and was continuing to consult with relevant unions and stakeholders to find an agreeable model.

But the committee set up to facilitate those negotiations has met just twice: in September 2012 and last month.

There was a ''staff consultation forum'' in June, which generated feedback on the needle exchange model. This feedback was taken to staff in December. Further consultation is planned for early this year.

But the union's regional director, Vince McDevitt, said the government was floundering, and brought nothing new to the table in the latest meeting.

He said that the needle exchange was still unworkable and jeopardised the safety of his members.

''They didn't bring anything new, they're scratching around like chickens, trying to find a different angle or a different approach, but they've been doing this for years now,'' Mr McDevitt said.

''The government needs to recognise there is insurmountable opposition to this, and for good reason.''

The government and the guards' union are preparing to negotiate a specific enterprise agreement for the prison.

Ms Gallagher's spokesman said there had not yet been any negotiation on changing any clauses in the agreement, which would include the condition requiring union support for the needle exchange.

The government said that no timeline had been set for the introduction of the needle and syringe program.

The delays have also frustrated supporters of the needle exchange.

Former ACT health minister and Public Health Association of Australia chief executive Michael Moore said he understood that the government needed time.

But he said it was sad to think about the consequences for prisoners and their families because of the lack of a needle and syringe program.

''It is frustrating that it's taking so long, on the one hand,'' Mr Moore said. ''On the other hand, we understand it would be the first such program in the English-speaking world, and as such it has to be done carefully and appropriately.

''But it is something that has to be driven, it won't just happen.''

Associate Professor Stuart Kinner, of the University of Melbourne's School of Population and Global Health, said the evidence for the effectiveness of prison-based needle exchanges was ''utterly compelling''.

Professor Skinner said there had been only one recorded incident in which a guard had contracted a blood-borne disease after being stabbed with a needle, and that occurred in a NSW jail with no needle exchange.

''The evidence is unambiguous and compelling that introducing a needle exchange in prison settings where there is a high prevalence of blood-borne viruses is an effective, low-risk public-health strategy that benefits everybody,'' he said.