The US president made the comments at a pro-gun rally, where he sought to justify gun ownership by comparing his own country’s record to a surge in knife crime in London at the start of the year.

Opponents accused him of sensationalising the issue in his speech to the National Rifle Association (NRA), where he said an unnamed London hospital was “like a war zone for horrible stabbing wounds” with “blood all over the floors”.

The row comes ahead of Mr Trump’s official visit to the UK in July, which was postponed earlier this year amid fears over large-scale protests over the president’s divisive agenda.

Speaking at the NRA convention in Dallas, Texas: “I recently read a story that in London, which has unbelievably tough gun laws, a once very prestigious hospital right in the middle is like a war zone for horrible stabbing wounds.

“Yes that’s right, they don’t have guns, they have knives. And instead there’s blood all over the floors of this hospital. They say it’s as bad as a military war zone hospital.”

While it is unclear what story Mr Trump was referring to, London surgeon Martin Griffiths told the BBC last month that some of his military colleagues had compared the levels of carnage they experienced at the Royal London Hospital to their time at Camp Bastion in Afghanistan.

Labour MP Sarah Jones, who chairs the all party parliamentary group on knife crime, posted on Twitter: “What a disgrace. Comparing apples and pears.

“Do we have a problem in the UK with rising knife crime? Yes we do.

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“Is is any way comparable to off-the-scale US gun violence? No, of course not. He should be ashamed.”

Professor Karim Brohi, a suergeon and director of London’s major trauma network, also issued a statement describing the claims as “ridiculous”.

Shadow home secretary Diane Abbott, MP for Hackney, tweeted: “Hardly see how violent crime in London justifies the licensing of guns in the US.

“Last month a leaked Home Office doc stated that it was Tory police cuts that “likely contributed” to a rise in serious violent crime.”

Scotland Yard has launched 55 investigations into suspected murders this year, of which at least 35 victims were stabbed to death.

The government faced questions over the role of police cuts in the surge in violent crime, as official figures show the number of officers has fallen by 20,000 since 2010.

Sutton and Cheam MP Paul Scully, Tory vice chair for London, told The Independent: “Knife crime is a serious issue and it is far too important to sensationalise.

“There is no excuse for bringing it into a debate about gun crime.

“It’s very unhelpful. It sensationalises an issue which costs lives and ruins families.”

Liberal Democrat former cabinet minister Sir Ed Davey called on Theresa May to explain the importance of the UK’s strict gun laws in reducing violent crime.

“London has seen a disturbing rise in knife and gun crime but Donald Trump’s remarks are nevertheless ridiculous,” the Kingston and Surbiton MP told The Independent.

“To defend America’s shocking gun laws by revealing his ignorance of Britain should alarm even his apologists in the Conservative Party.”

London mayor Sadiq Khan declined to comment on Mr Trump’s latest intervention, which comes after the pair publicly clashed over the terror attack in London Bridge last year.

UK news in pictures Show all 50 1 /50 UK news in pictures UK news in pictures 18 September 2020 A model presents a creation during the Bora Aksu catwalk show at London Fashion Week 2020 Reuters UK news in pictures 17 September 2020 World kickboxing champion Carl Thomas during his attempt to run a marathon while pulling a plane at Elvington Airfield near York. The attempt is raising funds for Ollie's Army Battling Against Battens, an organisation campaigning to raise GBP 250,000 to fund a clinical trial aimed at saving the sight of children with CNL2 Batten Disease PA UK news in pictures 16 September 2020 Labour deputy leader Angela Rayner speaking during Prime Minister's Questions UK Parliament/AFP/Getty UK news in pictures 15 September 2020 People enjoying the autumn sunshine as they punt along the River Cam in Cambridge PA UK news in pictures 14 September 2020 Early morning light bathes the skyscrapers of the City of London, at the start of a week in which the UK is expected to bask in temperatures of more than 30 degrees PA UK news in pictures 13 September 2020 England celebrate after they dismissed Australia's Alex Carey to win the second ODI match of the series at Emirates Old Trafford, Manchester PA UK news in pictures 12 September 2020 Protesters outside BBC Broadcasting House in central London, as marches and rallies form across the country calling for a 15% pay rise for NHS workers and an increase in NHS funding PA UK news in pictures 11 September 2020 An empty migrant dinghy floats off the beach at St Margaret's Bay after the occupants landed from France in Dover Getty UK news in pictures 10 September 2020 A view of small boats thought to be used in migrant crossings across the Channel at a storage facility in Dover, Kent PA UK news in pictures 9 September 2020 EU's chief negotiator Michel Barnier, left, arriving from the Eurostar with EU Ambassador to the UK, Portuguese diplomat Joao Vale de Almeida at St Pancras International railway station, London, for the latest round of the negotiations on a free trade deal between the EU and the UK PA UK news in pictures 8 September 2020 Dawn over Coquet Island, a small island off Amble on the Northumberland coast PA UK news in pictures 7 September 2020 A hovercraft arrives to Southsea, Hampshire from the Isle of Wight PA UK news in pictures 6 September 2020 Forensics officers near the scene of multiple reported stabbings in Birmingham Reuters UK news in pictures 5 September 2020 Anti-migrant protesters demonstrate in Dover against immigration and the journeys made by refugees crossing the Channel to Kent PA UK news in pictures 4 September 2020 Activists take part in a demonstration against the HS2 hi-speed rail line outside the Department of Transport AFP via Getty UK news in pictures 3 September 2020 Peter Baker, who plays Trigger in the musical version of Only Fools and Horses, sweeps the stage of the Theatre Royal Haymarket in London, after observing a 15 minute silence to show solidarity with those in the theatre industry that have lost their jobs due to the coronavirus pandemic PA UK news in pictures 2 September 2020 Kadie Lane, right, 11, and Brooke Howourth, 11, hug on their walk to Marden Bridge Middle School in Whitley Bay, Tyne and Wear, for their first day of term, as schools in England reopen to pupils following the coronavirus lockdown PA UK news in pictures 1 September 2020 Extinction Rebellion protesters sitting outside The Houses of Parliament in Westminster, London PA UK news in pictures 31 August Surfers at Long Sands Beach, Tynemouth PA UK news in pictures 30 August Black Lives Matter protesters march through Notting Hill in London in the first Million People March EPA UK news in pictures 29 August A protester reacts as she demonstrates against the lockdown and use of face masks, amid the coronavirus disease outbreak, outside Downing Street in London Reuters UK news in pictures 28 August Caribbean soca dancers display their costumes as they promote the first ever digital Notting Hill Carnival, following the cancellation of the normal Carnival festivities due to the continued spread of the coronavirus disease, in London Reuters UK news in pictures 27 August Father and son team Chris and Sam Milford from historic building conservation specialists WallWalkers begin restoration work on the spire of Norwich Cathedral, which stands at over 312ft high. 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The landmark's Twitter account confirmed only pedestrians and cyclists could use it on Sunday morning PA UK news in pictures 22 August England's Zak Crawley hit 267, joining the exclusive Double Hundred club, on day two of the Third Test match against Pakistan at the Ageas Bowl, Southampton PA UK news in pictures 21 August Harri Teale gathers lavender during the annual harvest on the Wolds Way Lavender farm near Malton in North Yorkshire PA UK news in pictures 20 August Parents and a student react after checking GCSE results at Ark Academy in London Reuters UK news in pictures 19 August Tate Modern workers hold a strike outside the gallery in London, to protest the institution's announcement that it would cut more than 300 jobs from its commercial arm, Tate Enterprises PA UK news in pictures 18 August Two rescued brown bear cubs, Mish (left) and Lucy, cool off in a pool after arriving at their new home with the wildlife conservation charity Wildwood Trust in Herne Bay, Kent. 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PA UK news in pictures 16 August Wasp players take a knee as Northampton Saints stand prior to kick-off in their Premiership match at Franklin's Gardens PA UK news in pictures 15 August Piper Colour Sergeant Lil Bahadur Gurung attends the VJ Day National Remembrance event, held at the National Memorial Arboretum in Staffordshire, Britain Reuters UK news in pictures 14 August People including students hold placards on Whitehall outside Downing Street as they protest against the downgrading of A-level results. The government faced criticism after education officials downgraded more than a third of pupils' final grades in a system devised after the coronavirus pandemic led to cancelled exams yes AFP via Getty UK news in pictures 13 August Benita Stipp (centre) and Mimi Ferguson (left) react as students at Norwich School receive their A-Level results PA UK news in pictures 12 August 2020 A train derailment near Stonehaven has left three people dead. 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The president berated Mr Khan for saying there was “no reason to be alarmed” by the armed police on the streets, but the mayor hit back, saying he was too busy to deal with Mr Trump’s “ill-informed” comments.

Mr Trump will make his long-awaited working visit to the UK on 13 July, and the US ambassador Woody Johnson that demonstrations would not deter the “thick-skinned” president from coming to London.