The Kremlin-backed news channel RT has lost a high court challenge to overturn a ruling by the UK media regulator that it broadcast biased programmes relating to the novichok poisoning in Salisbury and the war in Syria.

Ofcom fined RT £200,000 after determining that seven programmes, including two presented by the former MP George Galloway, were in breach of UK broadcasting rules relating to due impartiality regarding matters of political controversy.

The programmes fronted by Galloway, a regular presenter on the 24-hour news channel, covered the poisoning of the Russian ex-spy Sergei Skripal and his daughter Yulia in Salisbury two years ago. While the poisoning was blamed on Russia, Galloway cast doubt on the assertion.

Ofcom also found that four news and current affairs broadcasts addressing the US’s involvement in the Syrian conflict, and a news programme concerning the Ukrainian government’s position on Nazism and the treatment of Roma people, breached impartiality rules.

RT contended that Ofcom had not taken into account the fact that the “dominant media narrative” at the time of the poisonings – that Russia was to blame – meant it could leave that view out of its own programming. The broadcaster also said the requirement to be impartial interfered with its right to freedom of expression.

Lord Justice Dingemans, who delivered the high court judgment remotely on Friday, said the requirement for media to be balanced was paramount in the era of fake news.

“At present, the broadcast media maintains a reach and immediacy that remains unrivalled by other media,” he said. “Indeed, there is reason to consider that the need [for due impartiality] is at least as great, if not greater than ever before, given current concerns about the effect on the democratic process of news manipulation and of fake news.”

He saud RT was not restricted from broadcasting its point of view on the Salisbury poisonings, the war on Syria or events in Ukraine. “The only requirement was that, in the programme as broadcast, RT provided balance to ensure that there was ‘due impartiality’,” he said.

The judge said the “wider contextual factors” that RT relied upon to challenge Ofcom’s ruling were “not relevant and would serve to undermine the legislative objectives which the due impartiality regime is designed to safeguard”.

The judge said RT’s “concept of a dominant media narrative is a nebulous one, which it would be difficult to define, let alone identify by any acceptable criteria in a particular case.”

He added: “In any event the chilling effect that such uncertainty would or might produce for the broadcast media, would, in my judgment, be likely to inhibit rather than enhance their freedom of expression.”.

The judge also said there was “no error of approach” by Ofcom in reaching its ruling. “Ofcom’s decision as to breach and sanction were well within the applicable margin,” he said.

The high court said Ofcom’s ruling that RT was in breach of the broadcasting code followed a “long and detailed appraisal which paid careful attention to the rights of RT and the need for proportionality”.

An Ofcom spokeswoman said: “Trust in news and current affairs has never been more important, and RT’s failures to preserve due impartiality were serious and repeated. So we welcome today’s judgment that our investigation and decisions were fair and proportionate.”

An RT spokesman said: “We are aware of the court’s decision, and we intend to appeal.”