A West Australian bureaucrat has deemed the use of the term "Aboriginal" may be regarded as offensive and exercised a little-known power to redact it from birth, death and marriage certificates.

This means historians, native title claim groups and members of the public may be spending up to $49 to buy a document which may have historical detail like Aboriginality removed without their knowledge.

It has shocked historians, who were unaware of the practice and say Aboriginal is considered by most to be an inclusive term.

Aboriginal is a commonly-used term by governments around Australia, with several states — including WA — boasting ministers for Aboriginal affairs.

Emeritus professor of history at the University of Western Australia Jenny Gregory said she would write to the WA Attorney-General to request the practice be stopped.

Dr Gregory, who is also the president of the History Council of WA, said it was bizarre that the registrar of Births, Deaths and Marriages was determining what people could know about their ancestors.

"Way back in the past people might have hidden their Aboriginality … it's now a source of pride for many people of Aboriginal descent today," she said.

"In my view, and I think most historians would agree with this, the registrar is tampering with history.

"He's making, if you like, fake histories."

Practice stirs up painful memories

Like many other local historians contacted by the ABC, Dr Gregory was unaware that the registrar has the legislative authority to issue a certificate without a term they regard could be offensive.

It was brought to the ABC's attention by two keen family historians, Perth man Garry Smith and his Queensland-based cousin, John Chandler.

About five years ago, Mr Smith were researching his history online and discovered documents about to his father's aunt and grandmother, which referred to them as "Aboriginal Jane" and "Kitty Aboriginal".

He visited the Registry of Births, Deaths and Marriages in Perth to buy copies of the certificates and was horrified to discover the word Aboriginal had been whited out.

Mr Smith points to the original birth certificate using the label Aboriginal (left) and the redacted version (right). ( ABC News: Rebecca Turner )

He claims a staff member told him the term was offensive and had been removed.

Mr Smith, who does not consider the term Aboriginal offensive, was told he would have to fill out a statutory declaration to get a copy of the original document with the correct wording.

He said the experience made him feel sick, as if he should feel ashamed for being Aboriginal.

"If you're Aboriginal, it's offensive and deemed offensive — but the government calls us Aboriginals," he said.

For Mr Chandler, it was particularly painful to discover his identity in his middle-age and then have it removed by a bureaucrat.

He was brought up as "Spanish-Irish" because his grandmother refused to acknowledge her Aboriginal background after a painful childhood.

"We feel like we have people making decisions on behalf of us, just like in the past," he said.

The men want an apology from the registrar and for the practice to stop.

Root of decision unclear

Dr Cindy Solonec, an Indigenous colleague of Dr Gregory's on the History Council of WA, said she believed most Aboriginal people would be offended to know the term could be considered offensive and redacted.

"What a load of hogwash. We are Aboriginal people," she said.

The word "Aboriginal" is viewed by many of Aboriginal descent as a sign of pride.

Documents seen by the ABC suggest that the practice of removing terms deemed offensive began as part of the Registry of Births, Deaths and Marriages' digitisation of its records between 2007 and 2015.

It does not appear illegal under the legislation, which states:

"If, in the Registrar's opinion, a word or expression appearing on an entry in the Register is, or may be regarded as, offensive, the Registrar may issue a certificate under subsection (1)(a) without including the word or expression."

But it does raise questions about why the term Aboriginal was deemed offensive.

It is also unclear whether the current registrar, Brett Burns, or a predecessor made the decision. Mr Burns declined to be interviewed by the ABC.

He issued a statement which said that many details on certificates from the 19th and 20th centuries contained observations, which may have had no basis in fact and would be considered offensive, inappropriate and hurtful.

"Up until approximately the mid-1980s, when the registry began collecting reference to a person's Aboriginal or Torres Strait Islander origin at the request of the Australian Bureau of Statistics for statistical, medical and planning purposes (and not to be printed on a birth certificate), there has never been a legal requirement for registrars to note the race or ethnic background of a person on the 'Register' or such documents as birth certificates," the statement said.

"Some district registrars in the 1800s and 1900s entered such details on historical registers from personal observations which may have had no basis in fact.

"Many of these entries, though not all, would be considered exceedingly offensive, inappropriate and hurtful.

"Current legislation allows the registrar to remove reference to terms that may be offensive (or hurtful). That is why, and for no other reason, that birth certificates that reference Aboriginality is removed."

"This approach is consistent with practice across state and territory registries."

Aboriginal not the only 'offensive' term

Mr Chandler and Mr Smith also plan to lodge a racial discrimination claim against the registrar in the Federal Court, after an attempt at mediation by the Australian Human Rights Commission failed.

In correspondence to the AHRC in November last year, the WA State Solicitor's Office said other non-standard terms had been also removed from certificates because they were considered offensive.

"Other known words or expressions which may be regarded as offensive, disrespectful or hurtful include 'bastard', 'illegitimate' and 'incinerated' for cremated still-born babies," the office wrote.

"References to a person's race, such as 'Aboriginal' or 'Japanese' (particularly in pearling towns) were sometimes also recorded in birth registrations.

"Additionally, all these observations, words or expressions are redacted as they were not prescribed by regulation existing at the time and do not form part of the 'official' Register."

Both Dr Solonec and Dr Gregory said anyone who was researching their family tree, the most popular form of history in Australia, should be concerned about the amendment of certificates issued by the registrar.

"Loads of people are doing their family history and sometimes they find out some things that are shocking to them, other times they're delighted to find out information," Dr Gregory said.

"But the point is no one should change the past.

"This can't be changed and for the registrar to be able to prevent people from knowing who their ancestors are, seems to me an appalling state of affairs."