Britain today said it had repeatedly protested over a Holocaust-themed cartoon contest in Iran – but insisted it remains unclear whether it’s endorsed by the country’s authorities.

France, Germany, Israel and UNESCO are among those to have condemned the competition that was held nearly two weeks ago and featured images comparing Benjamin Netanyahu to Hitler among around 150 works featured.

Foreign minister Mohammad Javad Zarif has insisted the initiative – which carried a first prize of $12,000 – was run by a group “not controlled by the Iranian government”. But the Washington Post quoted a spokesman for the Ministry of Culture and Islamic Guidance as saying the ministry supports the exhibition and other programmes that “enlighten people about the Holocaust”. Supreme Leader Khamenei also reportedly expressed appreciation for the initiative.

The British government has condemned the contest in previous years and in its first comments on the controversy this year, a Foreign Office spokeswoman told the Jewish News: “We take very seriously any activities aimed at casting doubt on the existence of the Holocaust, wherever they occur in the world. The UK has made clear our concerns about Iran’s policies towards Israel and the Holocaust on many occasions.

“Our officials in Tehran have specifically raised our objections to this competition with the Iranian authorities several times during the past six months. However it remains unclear the extent to which the proposed Holocaust cartoon competition is officially sponsored or endorsed by the Iranian authorities.” The foreign office stood by the last line despite it not featuring in a subsequent statement on its website.

The contest was previously held during the presidency of Mahmoud Ahmadinejad, who has described the Shoah as a “myth”. But organisers insisted the contest was about highlighting Western double standards on free expression rather than denying the genocide.

“We have never been after denying the Holocaust or ridiculing its victims,” said Masuod Shojai Tabatabaei. “If you find a single design that ridicules victims or denies, we are ready to close exhibition.”

He added: “Holocaust means mass killing. We are witnessing the biggest killings by the Zionist regime in Gaza and Palestine.”

German foreign office tweeted this week: “We condemn exhibition with Holocaust cartoons in Iran in sharpest possible terms . Exhibition sows hatred and deepens divisions in the region.”