Salah Suhbi, a member of the House of Representatives, was among those calling for Mr Johnson to be dismissed after a controversial address to a fringe event at the Conservative Party conference.
When asked about a recent visit to Libya, where fighting continues six years after Britain’s intervention to oust Muammar Gaddafi, he praised the “incredible country” with “bone white sands”.
“There’s a group of UK business people, some wonderful guys who want to invest in Sirte on the coast, near where Gaddafi was captured and executed,” he added.
“They have got a brilliant vision to turn Sirte into the next Dubai. The only thing they have got to do is clear the dead bodies away.”
Mr Johnson laughed after the statement, which came after bloody battles to oust Isis from the city that had been its largest North African stronghold.
Mr Suhbi, a member of one of Libya’s two rival governments in the ongoing civil war, said: “It is cruel and unacceptable that the head of British diplomacy speaks and behaves in such a manner.
“Is this is a reflection of the British Government’s current views on Libya? Because this is not the UK that I know.”
Residents of Sirte are continuing efforts to rebuild the city, which was devastated in fighting that eventually saw Isis driven out in December.
Isis militants had overrun the city in 2015, following warnings that widespread conflict and lawlessness in Libya made it a ripe target for the group to spread terror training camps and take new strongholds.
Previously known as Gaddafi’s hometown and the place he was killed in 2011, the Mediterranean city was transformed into a theatre of oppression and brutality, with regular public executions and corpses left hanging or “crucified” in the streets.
Among those fleeing Isis’ rule was Yahia Atbiga, an engineer who The Independent met on a refugee rescue boat in the Mediterranean Sea last year.
“They kill people and then they hang their bodies up in the streets so people can see them, as a lesson to others,” he said at the time. “They shut everything down, I couldn’t stay there.”
Now in Germany, Mr Atbiga said he was shocked by Mr Johnson’s comments.
“He should know that people are looking for food and drink only now, but he is talking about transforming the city into Dubai,” he added.
“I think he does not know what he is talking about.”
Mr Atbiga said that after two rounds of conflict – in the first Libyan civil war and then against Isis – the remaining residents of Sirte were struggling even for the “simplest things of life” and many homes were reduced to rubble.
He was critical of David Cameron’s decision to support the Nato-led coalition bombing Gaddafi’s forces, amid fears of crimes against humanity committed against civilians during the Arab Spring.
The British Government confined its intervention mainly to air strikes and was heavily criticised for failing to support a future Libyan government as the country fractured following Gaddafi’s downfall.
Barack Obama accused the UK of allowing Libya to become a “shit show” after the dictator was removed, leaving two rival governments and thousands of militias battling for control as people smuggling triggered the start of the refugee crisis.
Mr Atbiga said: “I believe that the responsibility lies with both the international community and the countries participating in the war.
“They promised to support the people and achieve democracy, but the truth is quite the opposite – the destruction of the country and its fragmentation is what happened.
“I am sad for my country and I hope to see clear international support for the return of stability.”
Nader Elmeian, president of the Libyan Student Society at the University of Huddersfield, said Mr Johnson’s comments were not only offensive but factually incorrect, noting that there are no longer bodies in the streets of Sirte.
“I felt like he is disrespecting us and mocking Libya and the Libyans, which [is] bad from [a] person like him where he should try his best to help,” he told The Independent.
Politicians, including Conservatives, across the UK and around the world expressed their horror at Mr Johnson’s comments.
But the Foreign Secretary was unapologetic in a string of tweets, accusing people “with no knowledge of understanding of Libya [of] playing politics with the appallingly dangerous reality in Sirte”.
“The reality there is that the clearing of corpses of Daesh [Isis] fighters has been made much more difficult by IEDs and booby traps,” he wrote.
“That’s why Britain is playing a key role in reconstruction and why I have visited Libya twice this year in support.”
Damian Green, the de-facto Deputy Prime Minister, was among those rebuking Mr Johnson’s “unacceptable” comments.
He told BBC Radio 5 Live: “Let me be clear it was not an acceptable use of... it was not a sensitive use of language.”
Amber Rudd made clear she was losing patience with her colleague, branding him a “distraction”.
“I hope we can move on from that for now, until his next comment,” the Home Secretary told Sky News. “He’s a distraction sometimes, from the real stuff we are trying to do.”
Anna Soubry, a former Tory minister, said on Twitter that Mr Johnson is “embarrassing & PM should sack him” just days after another embarrassment in Burma.
Heidi Allen, a Tory MP who represents South Cambridgeshire, tweeted: “100 per cent unacceptable from anyone, let alone foreign sec. Boris must be sacked for this. He does not represent my party.”
Meanwhile, Conservative MP Sarah Wollaston told BBC Radio 4’s Today programme the remarks were “crass, poorly judged and grossly insensitive”, adding: “This is from the person who is representing us on the world stage… I think he should consider his position.“
The Shadow Foreign Secretary, Emily Thornberry, said Mr Johnson did not deserve his post if he thought the bloodshed in Sirte was a suitable subject for “throwaway humour”.
”It is less than a year since Sirte was finally captured from Daesh [Isis] by the Libyan Government of National Accord, a battle in which hundreds of government soldiers were killed and thousands of civilians were caught in the crossfire, the second time in five years that the city had seen massive loss of life as a result of the Libyan civil war,” she said.
“For Boris Johnson to treat those deaths as a joke, a mere inconvenience before UK business people can turn the city into a beach resort, is unbelievably crass, callous and cruel.
“If these words came from the business people themselves, it would be considered offensive enough, but for them to come from the Foreign Secretary is simply a disgrace.”
The furore was an unwelcome distraction for the Government during the Conservative Party conference, where Mr Johnson had already been accused of disloyalty for a high-profile newspaper interview giving Theresa May “red lines” on Brexit.
The Prime Minister has not publicly responded but a source at No 10 said she would “echo” Mr Green’s public rebuke, adding: “We didn’t feel it was an appropriate choice of words.”
But the source said that Ms May now regards the matter as closed and that if Mr Johnson chooses to apologise, “that is a matter for him”.
Additional reporting by PA
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