The secondary school teachers union ASTI has been warned it could lose the right to negotiate on behalf of its 17,000 members because of its failure to furnish audited accounts.
The union has been told it faces losing its charitable status - which gives it trade union negotiating rights - if it continues to withhold audited accounts.
The warning which was issued by the Registrar of Friendly Societies was made in a letter to the union, circulated in recent days to members of the union's executive or standing committee.
ASTI has been unable to provide the audited accounts for last year (due in June) because of a on-going dispute with the auditing firm Deloitte & Touche.
According to ASTI sources, the company claims it is still due fees for work conducted last year.
But one union source played down the importance of the letter from the registrar: "There is no question of the ASTI wilfully violating the rules. Some technical difficulties have arisen. But they will be resolved."'
An ASTI delegation will meet the staff of the registrar's office shortly in an attempt to resolve the problem.
The registrar has a supervisory role in respect of about 75 trade unions as well as co-operatives, credit unions and other bodies.
The ASTI conference voted earlier this year to replace Deloitte & Touche with a new auditing firm.
But the ongoing dispute with the company means ASTI accounts cannot be finalised.
In the past year, the ASTI has been riven by a bitter internal feud which has now become the subject of a High Court action.
Its general secretary, Mr Charlie Lennon has secured an interim injunction preventing the union from investigated alleged bogus expenses claims.
Mr Lennon claims the inquiry team - ASTI president, Mr Pat Cahill and vice-president, Ms Susie Hall - are prejudiced against him, a charge they vehemently deny.
In recent weeks ASTI has endured arguably the most difficult period in its history.
Members of its own head office staff have begun a Labour Court case against the union because of the continued non-payment of expenses and what they call the "intolerable" atmosphere in the union.
The union was also forced to rescind its ban on the new Junior Certificate science court after it was found to have breached the national pay deal by an arbitrator.