Donald Trump has used the latest terrorist attack in London to promote his beleaguered travel ban on residents of six Muslim-majority countries.

“Another attack in London by a loser terrorist,” the President tweeted, hours after an improvised explosive device detonated in the London subway system.

He added: “The travel ban into the United States should be far larger, tougher and more specific – but stupidly, that would not be politically correct!”

Later, in an appearance at the White House Rose Garden, Mr Trump said the country must be “smarter” when it comes to terrorism.

“It’s a terrible thing,” he said of the London attack. “It keeps going and going, and we have to be very smart and we have to be very, very tough – perhaps we’re not nearly tough enough.”

The US Supreme Court allowed a partial version of Mr Trump’s ban to be implemented in June. The ban has been plagued with legal challenges since its inception, with many claiming it amounts to an unconstitutional ban on Muslims.

The version of the ban permitted by the Supreme Court is Mr Trump’s second pass at the policy, which originally banned residents of seven Muslim-majority countries. The President has previously threatened to bring the full version of the ban before the Court.

The Supreme Court further amended the ban to allow foreign nationals with a “bona fide connection” to the US to enter the country. This includes students at US universities; employees of US companies, and parents, spouses, fiancés, children, siblings and half-siblings of people in the US.

The 9th Circuit Court of appeals recently expanded the list of relatives to include grandparents, aunts, uncles, and other extended family members. The Supreme Court, however, barred them from extending the list to include certain classes of refugees.

The Court will make their full ruling on the ban in October.

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Mr Trump has frequently used terrorist attacks to promote his ban, the formal title of which is “Executive Order Protecting The Nation From Foreign Terrorist Entry Into The United States”.

On 3 June, the day of the terrorist attack on London Bridge, the President tweeted: “We need to be smart, vigilant and tough. We need the courts to give us back our rights. We need the Travel Ban as an extra level of safety!” Officials had not declared the incident a terrorist attack at the time.

After Friday’s attack, which injured 22 people, Mr Trump tweeted that the “sick and demented” terrorists must be “dealt with in a much tougher manner”. Along with advocating for a “larger, tougher” travel ban, the President also suggested shutting down the internet.

“Loser terrorists must be dealt with in a much tougher manner,” he wrote. “The internet is their main recruitment tool which we must cut off & use better!”