Katie Hopkins’ departure from Mail Online came days after she gave a speech attacking Muslims and calling on people to “fight for their country”, it has emerged.
The publisher said the columnist’s contract “was not renewed by mutual consent” and Ms Hopkins did not respond to a request for comment.
News of her departure came three days after footage was published online showing her speaking at an event organised by far-right American think-tank the David Horowitz Freedom Center.
“It's such a pleasure to be amongst people that are prepared to fight for their country,” Ms Hopkins said, before telling the cheering audience it was “our time”.
“We can commit to arm ourselves, not just with the help of the NRA,” she added. “Get furious and fight back.”
The speech, made in Florida earlier this month, went on to claim areas of Britain were controlled by a “Muslim mafia” and allege that there was “institutionalised discrimination against whites” in the UK.
Ms Hopkins railed against “Muslim men” and the “Muslim mayor of Londonistan”, referring to Sadiq Khan, who she claimed she “cannot stand”.
She boasted of being reported to police for hate crime and inciting violence, before claiming she had expressed similar sentiments in a Mail Online column and making no allusion to her imminent departure.
Ms Hopkins, who rose to fame on reality show The Apprentice, previously wrote for The Sun as what the newspaper hailed as “Britain’s most controversial columnist”.
She also headed a programme on LBC Radio, which was ended – also apparently by mutual consent – in May.
That departure also came after listeners called police over a tweet calling for a “final solution” following the Manchester terror attack.
The message was deleted, with Ms Hopkins claiming the use of “final” was a typographical error and changing it to “true” in an apparent attempt to avoid comparisons to the Holocaust.
Campaigners have called for companies to stop advertising on the Mail Online website or with the Daily Mail newspaper, technically a different publication.
Donald Trump is among those to have praised Ms Hopkins’ writing, with the columnist in turn claiming she “loves” the US President.
The United Nations, by contrast, said a Sun column that saw Ms Hopkins describe migrants as “cockroaches” and “feral humans” resembled pro-genocide propaganda in 2015.
Ms Hopkins resigned and moved to the Mail Online – one of the world’s largest English-language news websites - five months later.
Update: A source at Mail Online said Ms Hopkins' contract ended last month, before the speech was made. Her final column was published on 5 October.