A former GB News presenter’s career was “killed” by Ofcom twice ruling his show breached its broadcasting code, the High Court has heard.

Mark Steyn is taking legal action against the regulator over its decisions in 2023 that two of his shows in 2022, which both related to the Covid vaccine rollout, amounted to breaches of its rules.

The Canadian broadcaster is asking a High Court judge to quash the decisions, with his lawyers claiming they lacked “clarity and coherence” and risked an “obvious potential chilling effect”.

However, barristers for Ofcom claim the regulator was free to make its decisions to protect the public from potential harm.

Speaking in a packed courtroom in London on Tuesday, Jonathan Price, for Mr Steyn, said: “The rulings against his show have killed his career, killed his career in the UK, and given rise to what he describes as crude defamation … recycled through the London papers as if they had the force of criminal convictions.”

The decisions related to two separate broadcasts of Mr Steyn’s primetime show on GB News, which began with the presenter delivering a monologue known as “The Steyn Line”.

Mr Price said that the show “did not adopt an anti-vax approach” but instead “strongly criticised the purely binary position” on Covid vaccines and featured guests who “questioned and challenged the official narrative”.

Ofcom’s first decision concerned a show broadcast on April 21 2022, which related to Mr Steyn’s monologue on the rollout of Covid vaccines, based on UK Health Security Agency (UKHSA) data.

The watchdog received four complaints about the broadcast and on March 6 2023 said it breached its rules as it “presented a materially misleading interpretation” of the figures “without sufficient challenge or counterweight”, which it said risked “harm to viewers”.

It also said that the programme “failed to reflect” that the UKHSA had warned that raw data on Covid vaccines “should not be used to draw conclusions about the effectiveness of the vaccine”.

The second decision concerned Mr Steyn’s show on October 4 2022, where he interviewed author Naomi Wolf.

Ofcom said in May last year that during the interview, Dr Wolf likened the vaccine rollout to a “mass murder” which was comparable to the actions of “doctors in pre-Nazi Germany”.

The regulator received 422 complaints following the interview, ruling on May 9 last year that GB News failed to take “adequate steps to protect viewers” from “potentially harmful content”, labelling Dr Wolf’s comments as promoting “a serious conspiracy theory”.

No statutory sanction was imposed for either breach, but GB News was requested to attend a meeting to discuss its approach to compliance with the code.

Mr Steyn, who no longer works for the channel, attended the hearing on Tuesday having travelled from the United States, with Dr Wolf also in attendance.

In a statement, Dr Wolf said that Ofcom had caused “incalculable” damage to her reputation through a “vague smear”, which she said was “false”.

In written submissions, Jessica Boyd KC, representing Ofcom, said there was “no realistic basis” for the court to rule that the regulator had “obviously gone wrong” in its decisions, adding that the rights of broadcasters to freedom of expression “are not unqualified”.

She said: “Both decisions were correct in concluding that the programmes could cause potential harm to the rights of viewers by distorting their understanding of issues which were likely to have a significant bearing on their health decisions in the context of a continuing pandemic.”

Ms Boyd continued: “Neither decision sought to prevent the claimant, or his guests, from ventilating controversial views about important public health issues or from challenging the reliability of official medical advice, including in inflammatory or provocative terms.

“He and they remain free to do so, provided they comply with the (Ofcom) code.”

The hearing before Mrs Justice Farbey is due to conclude on Tuesday, with a judgment expected in writing at a later date.