Kezia Dugdale has called on SNP politicians to “shun” a pro-independence blogger who has sent her a £10,000 claim for damages.
The Scottish Labour leader has accused Stuart Campbell, who runs the Wings Over Scotland website, of homophobia over a tweet.
Ms Dugdale hit out at SNP members for “encouraging” Mr Campbell on social media, asking them to “denounce” him.
Nicola Sturgeon “unequivocally” condemned “abuse of any kind”.
However, the first minister said Ms Dugdale’s questions were a “smokescreen” over the Aberdeen City Council coalition controversy.
Mr Campbell said he “categorically” rejected claims he was a homophobe, and said he would pursue the matter in court.
The Scottish Labour leader raised the issue during the weekly session of questions to the first minister at Holyrood.
She said she had been sent a letter from Mr Campbell’s lawyer after writing a newspaper column condemning a tweet he had posted earlier in the year about Conservative MSP Oliver Mundell, the son of Scottish Secretary David Mundell.
In it, he wrote: “Oliver Mundell is the sort of public speaker that makes you wish his dad had embraced his homosexuality sooner.”
Ms Dugdale said the blogger was seeking £10,000 for “damage to his reputation” after she accused him of homophobia.
She said: “I stand firmly behind my comments. I have never kow-towed to a bully and I will not start today.
“There is a catalogue of evidence that demonstrates the bile which Stuart Campbell appears to believe is acceptable. Will the first minister condemn Wings over Scotland and anyone else who poisons the political debate in our country?”
Ms Sturgeon replied: “I condemn anyone who indulges in that kind of language or that kind of abuse. I am not responsible for Stuart Campbell, any more than Kezia Dugdale is responsible for people who hurl abuse at me in the name of being a supporter of the Labour party.
“The abuse I see directed at me on a daily basis would make somebody’s hair curl and some of it does come from people professing to be supporters of Kezia Dugdale’s party. I do not hold her personally responsible for that. I think we should all accept that there are people out there who will do that and we should all unite in condemning it.”
Ms Dugdale went on to say that SNP politicians “continue to positively engage” with Mr Campbell, who she said “not only distorts our political debate but regularly spouts hatred”.
She said: “There are a few SNP politicians who have called him out, but 44% of SNP MPs and 50% of SNP MPs have actively encouraged him along. I have the list here and it includes 10 government ministers, the finance secretary, the justice secretary and the transport minister.
“I want to ask the first minister a clear yes or no question – will she today order her politicians and her own ministers to denounce and shun Wings Over Scotland once and for all?”
Ms Sturgeon repeated that she “unequivocally condemned” all abuse, but said Ms Dugdale’s line of questioning was “absolutely ridiculous”.
She said: “Let’s cut to the chase here, this is a smokescreen being erected by Kezia Dugdale today because her party is in disarray, it is civil war, it is in meltdown.
“She is directing this at me to hide one simple fact – as leader of the Scottish Labour Party she is not in control of her own party because she can’t stop her councillors going into coalition with Tories up and down the country.
“That is why she is asking about this today, as a smokescreen to protect herself against the state of her own party.”
Mr Campbell said the tweet was “obviously not homophobic any way”, but was a “criticism of Oliver Mundell’s terrible public speaking skills”.
He said: “I absolutely and categorically reject any accusations that I’m a homophobe – it’s an outrageous and completely false allegation and we’ll be pursuing the case in court.
“It’s correct that we initially offered to accept £10,000 for a quick settlement, but received no reply, and on the advice of counsel it’s likely that we’ll seek a higher figure, particularly now that Ms Dugdale has compounded the offence by repeating the defamatory statements on national television and involving the first minister.”