Speaking from Holyrood, the former first minister said she was not able to speak for her husband, Peter Murrell, who had served as the SNP's chief executive before he too was arrested and released without charge.

While Ms Sturgeon did speak briefly on Sunday after returning home, Tuesday saw her first major press engagement with the media since being arrested on Sunday 11 June.

Politics latest: Sturgeon 'searched her soul' over standing down

"It's not been the best period in my life," she told waiting reporters.

"It's not an easy period. I'm not saying that for sympathy… The thing that sustains me right now is the certainty that I have done nothing wrong."

Asked whether she would stand down from the party she was leading at the beginning of the year, Ms Sturgeon said will always consider what is best for the SNP.

She parroted a brief statement on Sunday, saying that she will "respect and fully understand the process that is under way. I am absolutely certain that I have done nothing wrong".

Pushed on whether she thinks everybody else has done anything wrong, Ms Sturgeon said: "This is a statement of facts, so don't read anything one or the other into this - I can only speak for myself in these matters.

"I'm here speaking for myself and, as I have done previously, expressing again my certainty that I have done nothing wrong."

As well as Mr Murrell, then SNP treasurer Colin Beattie was detained and released without charge earlier this year.

Police are investigating what happened to £600,000 raised by the party for independence campaigning.