A former SNP deputy leader has said Wendy Alexander should receive an apology amid the latest row over her Labour leadership campaign donations.
The Holyrood watchdog reported her to the procurator fiscal for not recording gifts to her leadership campaign in the MSPs' register of interests.
Former Nationalist MP Jim Sillars said the move was "astonishing".
But standards chief Dr Jim Dyer said he was required to take such action if any alleged rule breach may be an offence.
Ms Alexander, who became Scottish Labour leader in September last year, had initially been told she did not need to register the donations after seeking advice from the clerk to the Scottish Parliament's standards committee.
Labour said Dr Dyer - who operates independently from the committee - later informed the party this was "incorrect", prompting Ms Alexander to make a voluntary registration, detailing the donations.
The fiscal will decide whether the case merits a police investigation.
Mr Sillars told BBC Scotland: "If you refer someone to the procurator fiscal, you're implying that a criminal act has taken place.
"In my view, rather than refer to the [procurator fiscal], Mr Dyer should send an apology to Wendy Alexander. And I say that as a member of the SNP, not a Labour Party hack."
Dr Dyer said he could not comment on specific cases, but pointed out that he was not a "final arbiter" of what should be counted as a registerable interest.
That, he stated, was a matter for parliament or the courts.
The parliamentary standards commissioner went on: "When I investigate a complaint I have, however, to reach a view on whether there may have been a breach of the rules; if such a breach would, if proved, be an offence, I have to stop investigating and report to the procurator fiscal."
Meanwhile, despite Mr Sillars' comments, Ms Alexander dismissed fresh calls from the SNP for her to resign over donations to her leadership campaign.
The Scottish Labour leader told BBC Radio Scotland: "I don't think anybody's future should be called into question on the basis of following the advice of parliamentary authorities."
But SNP MSP Roseanna Cunningham said of Ms Alexander: "Her position as Labour leader in Scotland looks like it is nearing the endgame."
A Scottish Parliament spokesman said it had "no reason to believe" officials had given any MSP erroneous advice.
"The independent role of the Standards Commissioner means that he can take a different view - and therefore all advice from clerks is provided with the caveat that if a member is in any doubt, it is better to err on the side of caution and register," said the spokesman.
Meanwhile, the Electoral Commission is continuing to separately investigate an illegal £950 donation to Ms Alexander's campaign from Jersey-based businessman Paul Green.
It broke electoral law because he was not a UK voter.