Labour MSP Rhoda Grant has claimed a judge’s decision to dismiss the case of civil servant DeeAnn Fitzpatrick, who was taped to a chair at work, was a “miscarriage of justice”.

The politician, who has supported the former Marine Scotland worker for almost a decade, also refuted the suggestion that Ms Fitzpatrick had lied about the incident – despite a clear legal decision saying she was dishonest about the timing and nature of it.

Ms Fitzpatrick was dismissed from her role as a senior fishery officer after bosses decided she lied and falsified emails about the incident, which prompted a national outcry after a photograph of it went viral.

She claimed it took place in December 2010 after she reported an alleged assault on another member of staff, but a digital forensic expert found that the photograph was taken in August 2009.

She launched a case for unfair dismissal, but earlier this week an employment tribunal found in favour of Marine Scotland, with judge Alexander Kemp describing Ms Fitzpatrick as “dishonest”.

Ms Grant, MSP for the Highlands and Islands, said she was “deeply disappointed” with the decision and called for an independent inquiry into what went on.

She said: “I’ve known DeeAnn for well over a decade. I know she’s not dishonest. You couldn’t keep this up for that length of time.

“She’s been treated terribly, dragged through spurious disciplinaries, and in this case she had no legal representation and was up against the best that the Scottish Government could get.

“I think if any court of law knew what I know and had followed what I followed, they would know that this was a miscarriage of justice.”

She added: “I think the Scottish Government, right from the top – bearing in mind I have contacted Nicola Sturgeon about this – needs to look at their behaviour, how they treat their staff and deal with misogyny.

“We need an independent inquiry into all of this if the Scottish Government is going to learn any lessons from it.”

Several other workers claimed that the chair incident did not take place when Ms Fitzpatrick said it did, with some saying it was spoken about in a light-hearted manner in the body’s Scrabster office – including by her.

A digital expert also said it was “beyond doubt” that it was taken more than a year earlier.

However, while Judge Kemp dismissed the Canadian national’s claims about the incident, the tribunal described the office environment as “dysfunctional, if not corrosive” and one that had a “culture of puerile pranks”.

The Scottish Government said it would “reflect carefully” on the judgment and work to ensure its workplaces are “free from all forms of discrimination or harassment”.