A group of former Labour MPs have been called "cowards and traitors" on social media after quitting the party.
The seven faced calls on Twitter to stand down and trigger by-elections amid claims they were boosting the Conservatives by becoming independents.
Young Labour posted an emotive lyric from the socialist anthem, The Red Flag, to express its displeasure.
But deputy leader Tom Watson condemned those "celebrating" their exit and talking of "treachery and heresy".
And another Twitter user wrote that they admired the "fortitude" of Luciana Berger, one of the MPs to quit, given the anti-Semitic abuse she had suffered.
Ms Berger, who was one of the most prominent Jewish MPs in the party, cited the harassment she has received online as one of the main reasons for her quitting.
Announcing her decision to sit as an independent in Parliament, the Liverpool Wavertree MP said she was leaving behind a "culture of bullying, bigotry and intimidation".
In response, many Twitter users did not hold back in their criticism of the breakaway group, using phrases such as "splitters and Red Tories" to describe the seven.
Young Labour posted a short line from the Red Flag - the anthem traditionally sung at the end of the Labour party conference - to make it clear what it felt.
Though cowards flinch and traitors sneer, we’ll keep the red flag flying here.— Young Labour (@YoungLabourUK) February 18, 2019
Columnist and activist Owen Jones defended the criticism of the departing MPs, suggesting they had demonstrated they were out of step with Jeremy Corbyn's Labour party.
I haven’t sent a single Labour MP any “personal abuse”. Highlighting a politician’s political record - whether it be opposing LGBTQ rights or supporting privatisation - is not abuse, and it undermines the fight against actual abuse to claim otherwise. https://t.co/QGqcSpjaQS— Owen Jones🌹 (@OwenJones84) February 18, 2019
Rhea Wolfson, a former member of Labour's National Executive Committee, said the multiple resignations made her "angry" but urged fellow activists not to go over the top in their denunciation.
This self indulgent move is absolutely typical of why so many people have zero time for politics or politicians. Serving as an MP, representing a party, is a privilege. https://t.co/NzfHFLCLfY— Rhea Wolfson (@rheawolfson) February 18, 2019
In saying that, I think the 'good riddance' attitude is too simplistic. I have had a lot of respect for some of these MPs and I don't feel triumphant about this but I do feel angry— Rhea Wolfson (@rheawolfson) February 18, 2019
And Labour activist Paul Richards suggested the "tsunami of abuse and hate" being unleashed against the departing MPs had rather proved their point.
If I was advising Labour on comms I’d suggest that if MPs leave because of abuse and hate, unleashing a tsunami of abuse of hate on them might not be a great idea. But what do I know.— Paul Richards (@Labourpaul) February 18, 2019
Labour MP Neil Coyle said the party leadership needed to rein in what he described as "swaggering brocialists" who were "leading the pile-ons" against the MPs.
And Tom Watson posted a video message on Facebook saying that while he believed the MPs' actions were "premature", those glorying in their departure were wrong.
"This is a moment for regret and reflection, not for a mood of anger or a tone of triumph," he said.
Referring to the attacks on the MPs on social media, he added: "The tragedy of the hard left can be too easily tempted into the language of heresy and treachery."