Britain's homicide rate is a fraction of America's.
The President then mimicked a stabbing motion as he echoed the words "knives, knives, knives".
He added that "the Royal London Hospital has cut the number of our young patients returning after further knife attacks from 45% to 1%".
But Brohi, a fellow Royal London Hospital surgeon, stated, "To suggest guns are part of the solution is ridiculous". "Gunshot wounds are at least twice as lethal as knife injuries and more hard to fix".
Britain effectively banned handgun ownership after a 1996 school shooting.
Before he left, Mr Johnson said: "On so numerous world's foreign policy challenges, the United Kingdom and USA are in lockstep". "Trump gives the impression he couldn't give a fig".
Martin Griffiths, a surgeon at the Royal London Hospital, has spoken about young victims of violence after a spate of deadly crime in the city, which meant the number of suspected murders in March was higher than that of NY.
Comments by Trump have caused upset before in Britain. At least 35 people were fatally stabbed in London by April of this year.
It is true, however, that London has seen a recent spike in knife-related crimes. Baltimore, the deadliest American city in 2017, had a murder rate more than 45 times higher than London's, according to Federal Bureau of Investigation data.
"Happy to invite Mr Trump to my (prestigious) hospital to meet with our mayor and police commissioner to discuss our successes in violence reduction in London", he wrote.
The London Mayor's office declined to comment on Trump's latest remarks.
London comedy writer Robert Webb joked about his "war zone" city in a tweet.
Trump's absurd comments came ahead of his planned first presidential visit to the country on July 13. He's expected to be greeted with protests.
"They were brutally killed by a small group of terrorists that had guns". Boom! Come over here.
Attackers armed with assault rifles and suicide vests struck outside a France-Germany football match at the national stadium, cafes and bars, and the Bataclan concert hall in a coordinated assault that left 130 people dead and more than 350 wounded.
Former French president Francois Hollande and ex-prime minister Manuel Valls, who were in power at the time of the 2015 attacks, expressed their outrage in separate statements on Saturday.
"Every country freely decides on its own laws on carrying firearms, as in other areas".