A Scottish MP has apologised and will pay out £10,000 to charity after the threat of legal action by a man she called an "outed holocaust denier".
She agreed to pin an apology to the top of her Twitter feed for two weeks, but only hours after posting it made her profile private - meaning only those who already follow her can see it.
Mr Cameron hit out at her, posting his own message on the social media site saying the point of an apology being pinned was so that "people can see it". He also confirmed his solicitor had contacted Mrs McGarry.
The MP since appears to have made her apology accessible to those who do not follow her accessible.
The statement reads:
"On 6th March I tweeted that the Scotland in Union was headed by an 'internet troll' and an 'outed holocaust denier'. I made a serious mistake and accept there is no truth to those statements and apologise unreservedly to Mr Cameron for any distress caused."
As part of the agreement for no legal action to be taken further, Mrs McGarry paid £10,000 to charities Combat Stress, Aegis Trust and pro-Union campaigner JK Rowling's Lumos.
Mr Cameron wrote in response to news that the MP had agreed to apologise that he was looking forward to "drawing a line under this unfortunate incident".
"I am pleased to accept this apology from Mrs McGarry and draw a line under this unfortunate incident," he said in a statement.
"The payment Mrs McGarry has agreed to make will go to three excellent charities which I have been involved with and I am delighted that some good will now come of this.
"Politics in Scotland invokes passion and strong opinion on all sides, particularly on social media. I hope this serves as a reminder to us all that we need decency and respect in our debate, whether we agree with people or not.
"I look forward to continue making the positive case for Scotland in the UK."
McGarry has previously been threatened with legal action by JK Rowling herself, after the MP alleged that the author "defends abusive misogynist trolls".
After a long-running Twitter spat Ms Rowling wrote to Mrs McGarry: "You don't appear to understand how Twitter or defamation works. I'm going to help you out with the latter."