The MailOnline columnist tweeted: "22 dead – number rising. Schofield. Don't you even dare. Do not be part of the problem. We need a final solution. #Machester."
Hopkins hastily deleted the tweet, changing "final" to "true" and corrected the spelling of Manchester – but not before it had been noticed and screen-grabbed by several sources.
The original comment has been interpreted by some to refer to the Wansee Conference held in January 1942, attended by high-level Nazi party and German governmental officials where the decision was taken for a 'Final Solution to the Jewish Problem'. What followed were mass killings at death camps in Auschwitz, Treblinka and Sobibor.
Hopkins responded to queries about the revision, claiming: "I stand by my tweet. I find the typo disrespectful to the survivors of Manchester."
But commentators were quick to brand the mother-of-three a "Nazi" and accused her of calling for a mass genocide. Political activist and commentator Owen Jones called for a boycott of LBC until Hopkins is sacked.
He wrote: "LBC depends on guests to function. Until they sack Katie Hopkins we should all boycott all interview requests. Enough is enough. A national radio station is employing someone who calls for genocide. Don't say 'just ignore her, she'll go away', because she won't."
Writer George Monbiot tweeted his support: "I agree. @LBC, please don't ring me until she's gone."
Others joined calls to LBC to take her off the air and HuffPost UK has sought comment from the radio station.
Sandra Pickering said she had reported Hopkins to the police, while David Smith wrote: "Have seen tweet(s) from Katie Hopkins. Have reported her to Met Police. UK tweeps may wish to consider doing the same." A spokesman for the force confirmed a complaint had been received and that the allegation was being reviewed and assessed by specialist officers.
Last month Hopkins was reported to the police after remarks she made in the wake of the arrest of a man in Whitehall on suspicion of plotting a terror attack. She was accused of a hate crime after tweeting: "Explosion in France, shooting at a German hospital, knife attack in London. And Ramadan has not yet begun. Without food these sods get nasty."
It's believed she was referring to an explosion at a McDonald's restaurant in the south of France and a shooting at a hospital in Berlin, also on Thursday. Neither incident was believed to have been linked to terror. The Met confirmed the allegations were being investigated.
In March Hopkins lost a Twitter libel case against food blogger Jack Monroe. Monroe won £24,000 in damages, while Hopkins was ordered to pay both her own and Monroe's legal bills, a figure some experts say could exceed £300,000. The action was over a tweet sent by Hopkins in 2015 which implied Monroe had either vandalised a war memorial or had condoned the act.
In 2015 she escaped charges over allegations she had incited racial hatred for calling migrants "cockroaches." She was questioned by police in connection with the controversial column, published in The Sun on April 17, that came in the wake of a capsizing in which 400 migrants are believed to have drowned.
The piece, entitled 'Rescue boats? I'd use gunships to stop migrants', likened people fleeing war-torn nations to "cockroaches" and called for them to be turned away with military force.
A day later up to 900 people were feared to have lost their lives after a similar incident. The UN High Commissioner for Human Rights said the language the reality TV star had used in her column was similar to that used by newspapers and radio stations in Rawanda before the 1994 genocide that led to hundreds of thousands of people being slaughtered.
Jordanian Zeid Ra'ad Al Hussein urged authorities in the UK to use the law to clamp down on "vicious verbal assault on migrants and asylum seekers in the UK tabloid press", adding: "The Nazi media described people their masters wanted to eliminate as rats and cockroaches. This type of language is clearly inflammatory and unacceptable, especially in a national newspaper.
Hopkins was reported to the Met three days after the article was published by Society of Black Lawyers chairman Peter Herbert, who complained her words were "offensive" and "xenophobic."
The Special Enquiry Team of the Homicide and Major Crime Command investigated, but six months later Hopkins revealed she had been given the all clear. She told MailOnline: "I will not and will never apologise for standing up for what I believe in.
"I find it surprising that at a time when police are so undermanned they can't afford to turn up to burglaries or find cars after a crash, they think a woman with an opinion is their highest priority.
"I am grateful Scotland Yard enjoys my writing but I would encourage them to focus their energies on those who present a real threat to this country which I love.