The communications manager of Sheffield Hallam MP Jared O'Mara has resigned in a flurry of angry tweets published on the MP's own Twitter account.
Gareth Arnold - a member of Mr O'Mara's constituency staff - accused him of showing "inexcusable contempt" for constituents.
Among the posts was one that read: "Jared, you are the most disgustingly morally bankrupt person I have ever had the displeasure of working with."
The BBC has asked Mr O'Mara to comment.
The Twitter thread continued: "Sheffield Hallam deserves so much better than you. You have wasted opportunities which people dare not to even dream of."
The thread told the MP to "call a by-election" and informed Mr O'Mara he should consider the Twitter posts as Mr Arnold's "resignation".
Mr O'Mara, 37, quit the Labour party in July 2018 after being suspended over alleged misogynistic and homophobic comments posted online.
His victory against former deputy prime minister Nick Clegg in the Sheffield Hallam seat was one of the shocks of the 2017 general election.
Mr Arnold, who describes himself as a blogger and a digital marketing professional, rose to prominence in 2014 when he set up a social media account called Britain Furst which was intended to troll the right-wing political group Britain First.
The following year he set up a satirical news website and posted fake news articles mocking tabloid titles.
'Horrible thing to do'
He told BBC 5 Live that he had been working for Mr O'Mara for eight weeks but had known him "for absolutely years".
When asked about the method of his resignation, he said: "I appreciate from the outside it looks like a really horrible thing to do."
But he added: "We're left with a situation where there's people in Sheffield Hallam who are not being represented.
"There are people who are waiting on their immigration status, there are people who are not getting houses, there are people having their benefits stopped and all these things stopped just because he's not prepared to do his job properly.
"Yes it was a ridiculous statement but it's the one thing I think might motivate change."
Well, I can't sleep. Did I do the right thing? Did I go the right way about it? Did I act in anger and frustration? I expect I'll come to learn these things soon.— gareth (@garetharnolduk) July 24, 2019
Following his resignation, Mr Arnold took to his own account and tweeted: "Well, I can't sleep.
"Did I do the right thing? Did I go the right way about it? Did I act in anger and frustration?
"I expect I'll come to learn these things soon."
Mr O'Mara, who now sits as an independent, told the BBC earlier this month that he intended to stand for election again despite criticism of his voting record.
"I am going nowhere, and I'm here for you whether you want me here for you or not." he said at the time.
"With the support of those around me and with renewed vigour, I'm standing again next time."
In April Mr O'Mara closed his office while he recruited new parliamentary staff and moved buildings, leaving his constituents unable to contact him for several weeks.