British officials face being banned from the United States if they are found to have breached the free speech rights of American citizens.
US secretary of state Marco Rubio said foreign officials "complicit in censoring" American citizens and media companies will be denied entry to the US.
The visa ban could apply to individuals working for Ofcom, which is the regulator responsible for policing Britain's online safety laws.
The US State Department has repeatedly raised concerns over the laws' capacity to curtail freedom of expression.
The announcement is understood to have taken British officials by surprise with diplomats seeking clarity from the White House.
Marco Rubio could put the foot down on the policy
Reuters
Announcing the measure, Rubio said: "For too long, Americans have been fined, harassed, and even charged by foreign authorities for exercising their free speech rights."
"It is unacceptable for foreign officials to issue or threaten arrest warrants on US citizens or US residents for social media posts on American platforms while physically present on US soil," he said.
He went on to highlight: "It is similarly unacceptable for foreign officials to demand that American tech platforms adopt global content moderation policies or engage in censorship activity that reaches beyond their authority and into the United States."
"We will not tolerate encroachments upon American sovereignty, especially when such encroachments undermine the exercise of our fundamental right to free speech."
Secretary of State Marco Rubio
Reuters
Britain's online harms laws have drawn the ire of free speech advocates and economists, who warn their broad provisions to tackle harmful online content could lead to excessive censorship prevent deter investment from American tech giants.
The Online Safety Act is despised by Donald Trump's administration because of the massive fines it can levy on US tech companies.
Under the law, social media giants face fines of up to £18 million or 10 per cent of their annual revenue if they fail to remove harmful content from their platforms.
"In some instances, foreign officials have taken flagrant censorship actions against US tech companies and US citizens and residents when they have no authority to do so," Rubio said.
WATCH: Ben and Dawn discuss news Donald Trump will pressure Keir Starmer over Lucy Connolly Southport tweet case
In the aftermath of the Southport attack in which Axel Rudakubana murdered three girls at a Taylor Swift-themed holiday club, officials threatened to arrest, prosecute and extradite American officials who violated hate speech laws.
"We will throw the full force of the law at people. And whether you're in this country committing crimes on the streets or committing crimes from further afield online, we will come after you," Sir Mark Rowley, the Metropolitan Police Commissioner, said at the time.
Republican commentator Charlie Kirk told GB News the case of Lucy Connolly, a mother who was jailed for a social media post, has been raised in the White House.
Connolly, 42, a wife of a Conservative councillor, was sentenced to 31 months in prison after pleading guilty to inciting racial hatred following the Southport stabbings last year.
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