And concerns have been raised about the process that led federal workplace authority Comcare and its lawyers to bring the men's evidence to a Canberra Public Service bullying hearing last month.

The tribunal said in a published decision that the credibility of Comcare's main witnesses in the case, two senior public servants, both of whom faced complaints in the case, was ''in issue''.

Tribunal member Simon Webb wrote in his decision that it was ''mystifying'' and ''a matter of concern'' how top-end law firm DLA Piper and its barrister did not spot ''striking similarities'' in sworn statements of Radha Sharma and his ATO supervisor Ahmed Hijazi before Comcare's legal team presented the evidence to the tribunal.

Mr Webb found that Comcare's denials that an EL1 bureaucrat in the Tax Office suffered a psychological injury after being bullied by her superiors were undermined by ''serious unresolved questions about collusion, inconsistencies and the selective production of documents''.

The tribunal found Dimitra Michalopoulos, a 25-year public service veteran, suffered her injury as a result of her treatment at the Tax Office in 2010 and set aside Comcare's finding that the conduct of her superiors was ''reasonable administrative actions'' to address performance issues. The tribunal member wrote that it was very suspicious about the sworn statements supplied by two of Ms Michalopoulos's superiors, her boss Mr Sharma and his supervisor Mr Hijazi, which were identical in parts.

''It is simply inconceivable that the identical passages, attachments, interpretations and omissions are the result of coincidence, and it is disingenuous to hold this out as a serious explanation,'' Mr Webb wrote.

''It is very clear is that the accounts given by Mr Sharma and Mr Hijazi about the creation of these statements cannot both be true; somewhere in their sworn evidence there is a lie, or perhaps an omission

or an error. I accept that Mr Sharma and Mr Hijazi may not have been able (or willing) to provide a cogent explanation, but it is quite clear that the identical passages, attachments, interpretations and omissions are not the product of an accident; they indicate deliberate action taken by Mr Sharma or Mr Hijazi.

''Who is in error or at fault, whether one or both witnesses, I am unable to determine.''

Ms Michalopoulos said she went to her superiors in April 2010 with a complaint about a contractor in her team who she alleged ''was prone to yelling, shouting and screaming'' at her and fellow workers.

Her complaint against Mr Sharma was that he bullied her, with the backing of Mr Hijazi, by failing to support her and raised ''performance issues'' after she complained.

The AAT does not specify the nature of Ms Michalopoulos' complaint against Mr Hijazi.

Mr Webb said that Comcare's case weighed heavily on the words of the two senior managers and there were serious doubts about the credibility of their evidence.

''There are doubts about the reliability of substantial evidence given by Mr Sharma and Mr Hijazi,'' Mr Webb wrote. ''Close examination of their evidence raises serious unresolved questions about collusion, inconsistencies and the selective production of documents.

''The specific issues pressed by Comcare require Ms Michalopoulos' evidence to be weighed against that given by Mr Sharma and Mr Hijazi.

''Rightly or wrongly, Mr Sharma and Mr Hijazi are both the subject of complaints by Ms Michalopoulos.

''It is quite clear that the reliability and credit of these witnesses is in issue.''

The tribunal member also questioned the process that led Comcare to rely on the evidence from the two men.

''The processes Comcare applied when providing instructions in this case, and the content of advice it obtained from its retained solicitors and counsel, are matters for it,'' Mr Webb wrote.

''But to my mind these aspects of the case raise issues for Comcare to reflect upon.''