Lisa Cameron announced on Thursday she was quitting the SNP for the Conservatives.
The SNP’s president has described the defection of one of the party’s MPs to the Conservatives as an “odd tantrum”.
Lisa Cameron announced on Thursday she would cross the floor, blaming a “toxic” culture in the SNP’s Westminster group.
Dr Cameron said she had required counselling after standing up for the young staffer harassed by MP Patrick Grady, claiming she was shunned by colleagues.
Speaking to BBC Radio Scotland on Friday, SNP president Mike Russell said the move was “bizarre”.
He said: “What the SNP needs to do is focus on the big issues in Scotland, not what seems to be a rather odd tantrum from somebody who was going to lose their nomination.”
Dr Cameron was facing a selection battle in her East Kilbride, Strathaven and Lesmahagow seat from SNP staffer Grant Costello, who was supported by both Scottish Government minister Christina McKelvie and current and former East Kilbride MSPs Collette Stevenson and Linda Fabiani.
The outcome of the selection was due to be announced on Thursday, hours after Dr Cameron revealed she would leave the party.
Ms Russell continued: “It was absolutely clear the constituency party had lost faith in her, and I think that kind of ego drive politics is deeply unattractive.”
The defection was downplayed by First Minister Humza Yousaf on Thursday, who told the PA news agency it was the “least surprising news” he had heard since taking the top job earlier this year as he said Dr Cameron “probably never believed” in Scottish independence.
Both the First Minister and Mr Russell said Dr Cameron should step down and force a by-election in the seat.
Mr Russell also rejected claims there was a toxic culture in the party’s Westminster group, saying: “I don’t agree with those claims.
“I think these are claims but I think these are unsubstantiated claims.”
He went on to say he had “no idea” if Dr Cameron sought counselling as a result of her treatment at the hands of the Westminster group, adding: “I’m sorry that is the case, but I don’t believe – certainly from what I’ve heard – that the sole reason for that was something to do with the Westminster SNP group.
“I have to say, I have the greatest sympathy for anybody in those circumstances, but their claim as to how they arose… that claim does have to be, regrettably, examined and I do not believe there is a toxic culture in our Westminster group.”
Appearing on the same programme, Scottish Tory chairman Craig Hoy hit out at Mr Russell’s comments.
He said: “I listened to Mike Russell this morning on your programme, dismissing the concerns that had been raised by Lisa Cameron in the most high-handed of ways, dismissing the fact that there is a toxic culture within the SNP, despite the fact that I think everyone can see that laid bare.”
Asked if it was “bizarre” Dr Cameron chose to leave the leading pro-independence party for the leading pro-union party, Mr Hoy said it was not, and that he was “delighted” she had crossed the floor.
Asked if Dr Cameron still supports independence, Mr Hoy said:” To join the Scottish Conservative and Unionist Party, you have to recognise that you believe in the four constituent parts of the UK, moving and working together.”
