Autism New Zealand is set to enter mediation after disestablishing its Auckland branch committee, unhappy with communication, abuse of power and running of programmes "not endorsed" by the parent body.

The two parties met in late August to try to reach a compromise after the Christchurch head office learned of Auckland's plans to move to new premises in Albany, and demanded to know more details.

Autism NZ is a support group for sufferers of autism, Asperger syndrome and associated disorders. It has 15 branches nationwide, and a membership of more than 4000.

Minutes from the August 31 meeting show the national board held "serious concerns about the Auckland branch acting outside the approved delegations" by committing itself to long-term leases for property, furniture, equipment and vehicles.

It was also concerned about Auckland's failure to report branch business dealings "in a timely manner", and "promoting services not endorsed by Autism NZ".

The national body subsequently disestablished the Auckland branch, citing the reasons in a September 29 letter to Autism NZ members.

But the Auckland branch intends to continue with its Albany branch office, leaving the St Lukes office under the interim control of the Autism NZ national board, documents show.

In a letter of its own to society members, the Auckland branch committee expressed its "shock" at the national body's actions.

"We were led to believe we were moving forward with the board of Autism NZ, after a meeting was held on August 31 ... This appears not to have been the intention, and motives for forcing the meeting insincere."

None of the parties to the dispute were willing to discuss the row, including Autism NZ president Wendy Duff, who said she was "disgusted" that the matter had become public.

Auckland branch chairwoman Mary Henderson refused to give any details of the unapproved "services" being offered, or discuss the coming mediation.

Hamilton doctor Bill Reeder - who has studied autism and worked with members of both the Auckland and national organisations - said the Auckland branch members had been supporters of biomedical treatments, many of which had been studied for more than 25 years.

Biomedical treatments for autism focus on treating physical problems often common in autistics, such as gut complaints, to relieve symptoms.

Normal treatments focused on behavioural or drug therapies, Dr Reeder said.

Autism NZ correspondence to members shows the organisation was concerned about Auckland's "move towards services that the board is not in a position to endorse (for example, the medical aspects of biomedical treatments)".

Mrs Henderson said the acquisition of a new building in Albany was "just a part of expansion under a Ministry of Health contract".

She downplayed the feud between the Auckland branch and Autism NZ headquarters.

"All is well and good. Everyone is here for the good of the members. These are just a few areas we need to come to agreement on and move forward."

It is understood the two parties will go to mediation on Monday.