The name of an Australian soldier killed in Vietnam was added to the Australian War Memorial's Roll of Honour in the interests of official commemoration even though it was against his family's wishes.

Freedom of Information documents obtained by Fairfax Media reveal that Private Dal Abbott's name was always intended to be added to the Roll "at an appropriate stage".

The family of Private Dal Edward Abbott, killed on May 30, 1968, did not want his name to be added to the Honour Roll because it was a war they strongly opposed.

According to Private Abbott's sister Lynne Peterson, it was also because "my parents just didn't want him remembered in those terms [as a soldier]".

While the AWM at first agreed to the family's request, Private Abbott's name was placed on the roll last May.

In a letter to the Abbott family written after the decision to add Dal Abbott's name to the Roll, current AWM Director Dr Brendan Nelson wrote that the decision "was motivated by the belief that after 45 years, it is time for his country to honour his sacrifice".

The letter referred to the belief that the AWM Act ensured the institute's governing body is "the sole arbiter in relation to the listing of names on the Roll".

But the AWM Act of 1980 makes no mention of the Honour Roll nor does it specifically refer to how deceased soldiers' names can be used.

Leading military historian and former head of history at the AWM, Professor Peter Stanley, said  Dr Nelson "cannot use the Act to prescribe in that way", adding, "common decency should have prevented him from doing so".

He said Private Abbott's case raised questions about the nation's culture of military remembrance. It has special relevance as Australia prepares for the Gallipoli centenary next year.

Lynne Peterson said her brother's story said the AWM's decision showed how personal and family grief can be subsumed by the perceived needs of national memory and official history.

She said there should be more certainty for families in relation to the use of deceased soldiers' names to "make it more dignified and rational than what we've been through".

"It would give people in our situation clarity.''