Ms Alexander spoke out after it emerged Dr Jim Dyer, the Scottish Parliament's standards watchdog, sent a report to the procurator fiscal in Lothian and Borders.

It means Ms Alexander now faces the possibility of a criminal investigation if the procurator fiscal then refers the matter on to the police.

On Friday Ms Alexander publicly declared the top donors to her leadership campaign, naming 10 supporters who each gave just under £1,000. She explained she was disclosing their details after advice from Dr Dyer, the Scottish Parliamentary Standards Commissioner.

Ms Alexander, who became Scottish Labour leader in September, had initially been told she did not need to register the donations on Holyrood's register of MSPs' interests.

But Labour said Dr Dyer later informed them this was "incorrect", prompting Ms Alexander to make a voluntary registration, detailing the donations.

In a statement Ms Alexander said the Standards Commissioner had to refer the case to the procurator fiscal automatically.

She added: "I am clear that suggestions that I have been guilty of trying to subvert the law in the registration of donations are completely unfounded. I am also very clear that the Labour Party and Scottish politics would be ill-served by my resignation.

"Despite the smears and accusations from my political opponents, I will not stand down for having followed the Parliamentary authorities' guidance."

A spokeswoman for the Crown Office confirmed that a report had been received by the area procurator fiscal for Lothian and Borders and that this was now being considered.