The Fiji Human Rights Commission says the interim administration's plan to reduce the retirement age of public servants to 55 years is against provisions of the 1997 Constitution.
The Constitution forbids discrimination based on age or any other characteristic.
The Commission director, Dr Shaista Shameem, says the plan is also contrary to a High Court ruling delivered in November last year based on the constitution.
Dr Shameem says only a law can impose an age limit but there is no such law.
She says any such law would have to cover all holders of public office - not just public servants.
Fiji's President Iloilo is 85 while judges do not have to retire until they reach 70.
Dr Shameem says the Commission will seek a meeting with the interim attorney general to explain the meaning of the High Court ruling and constitutional provisions for the information of the interim cabinet before it makes a decision on compulsory retirement.
The general secretary of the Fiji Teachers Union, Agni Deo Singh, has welcomed the plan to lower the retirement age, saying it will create jobs for newly qualified teachers but the mainly indigenous Fijian Teachers Association has strongly opposed it.
Fiji's military has warned the general secretary of the Public Service Association, Rajeshwar Singh, to stop threatening industrial action over the plan and to enter into talks with the interim administration if he has any problems.