In a statement, GB News insisted the Prime Minister had been questioned “robustly, intelligently and freely” by viewers and branded Ofcom’s finding an “alarming development in its attempt to silence us”.

It added: “The regulator’s threat to punish a news organisation with sanctions for enabling people to challenge their own Prime Minister strikes at the heart of democracy at a time when it could not be more vital.

“Ofcom is obliged by law to uphold freedom of speech and not to interfere with the right of all news organisations to make their own editorial decisions within the law.

“Its finding today is a watershed moment that should terrify anyone who believes, as we do, that the media’s role is to give a voice to the people of the United Kingdom, especially those who all too often feel unheard or ignored by their politicians.”

In its ruling, Ofcom said it recognised that Conservative viewpoints would be prevalent given the nature of the programme, but said it was incumbent on GB News to ensure that an appropriately wide range of views were shown.

It found that while some of the questions from the audience provided some challenge to, and criticism of, government policies, the audience was not able to challenge Mr Sunak’s responses, nor did the presenter do so.

Ofcom said the Prime Minister criticised aspects of the Labour Party’s policies and performance, but Labour’s views were not reflected in the programme. 

It added that Mr Sunak was able to put forward future policies his Government planned to implement if re-elected, but that these were not challenged.

It marks the latest in a string of impartiality breaches by GB News. In March, Ofcom found that five programmes hosted by MPs including Sir Jacob Rees-Mogg were in breach of rules governing the use of politicians as presenters.

Ofcom had previously put GB News on notice because of its lack of compliance with broadcasting rules. The watchdog will now decide whether to issue the channel with a fine and will publish its decision within 60 working days.