He is understood to be based in the US and faces being deported while Clare Melford, of the Global Disinformation Index (GDI), will have her visa revoked.

A French ex-EU commissioner and two senior figures at a Germany-based anti-online hate group were also denied visas.

French President Emmanuel Macron led European condemnation of the move, describing it as “intimidation”.

The US billed the measures as a response to people and organisations that have campaigned for restrictions on American tech firms, with Secretary of State Marco Rubio saying they belonged to a “global censorship-industrial complex”.

He said: “President Trump has been clear that his America First foreign policy rejects violations of American sovereignty. Extraterritorial overreach by foreign censors targeting American speech is no exception.”

Mr Ahmed, from Manchester, is the chief executive of the Centre for Countering Digital Hate (CCDH). The organisation has previously listed Sir Keir Starmer’s chief of staff, Morgan McSweeney, as a director.

Mr Ahmed previously told the Triggernometry podcast that the origin of CCDH came while working as an adviser to Labour MP Hilary Benn, who was shadow foreign secretary at the time.

He has said he was inspired to start the organisation after seeing the rise of antisemitism on the left in the UK and the murder of his colleague, Jo Cox MP, by a white supremacist, who was radicalised, in part, online.

Records at Companies House show Mr McSweeney resigned from CCDH in April 2020, the time at which Sir Keir became leader of the Labour Party.

Elon Musk also declared “war” on the CCDH in October 2024, branding it a “criminal organisation”.

Thierry Breton, the former top tech regulator at the European Commission, was also targeted. Also subject to bans were Anna-Lena von Hodenberg and Josephine Ballon of HateAid, a German organisation that the State Department said helped enforce the EU’s Digital Services Act (DSA), which imposes content moderation on social media firms.

A GDI spokesman said that “the visa sanctions announced today are an authoritarian attack on free speech and an egregious act of government censorship”.

“The Trump Administration is, once again, using the full weight of the federal government to intimidate, censor, and silence voices they disagree with. Their actions today are immoral, unlawful, and un-American.”

A UK Government spokesman said: “The UK is fully committed to upholding the right to free speech.

“While every country has the right to set its own visa rules, we support the laws and institutions which are working to keep the internet free from the most harmful content.

“Social media platforms should not be used to disseminate child sex abuse material, incite hatred and violence, or spread fake information and videos for that purpose.”