Campaigners are calling for an advertising boycott of Facebook in the US to be extended to Europe, after its chief executive, Mark Zuckerberg, dismissed the effects of the campaign in a meeting with staff.

A growing number of companies have halted advertising on Facebook after criticism that the platform was not doing enough to counter hate speech on its sites.

Imran Ahmed, the chief executive of the British nonprofit the Center for Countering Digital Hate, said: “There’s a very strong argument to be made that advertisers should be boycotting Facebook in Europe as well.

“In the US, I think the question of Facebook’s role in spreading hate is highly party political, but in Europe it’s generally accepted on all sides as being a serious problem.

“Perhaps that’s taken some of the fire and energy out of calls for Facebook to change its behaviour. But most of the polling shows that in Europe there is an even stronger desire for Facebook to be held to account for the hate speech and misinformation that spreads on its platform.”

In response to criticism, Zuckerberg last month announced a raft of changes to the platform’s hate speech policies, banning content that demonises immigrants and further restricting posts that make false claims about voting.

While some advertisers, including Patagonia and Ford, have pulled spending internationally as part of the campaign, others such as Unilever have only taken action in the US. The UK-headquartered conglomerate, which owns brands including Ben and Jerry’s and Marmite, explained its decision with reference to the “polarised election period in the US”. Unilever has not responded to requests for comment.

In the past week, many of the companies that joined the boycott announced they would pull all spending globally. Lego’s chief marketing officer, Julia Goldin, said the company would “take immediate steps to carefully review the standards we apply to advertising and engagement on global social media platforms”, and would pause all spending for 30 days. “We are confident solutions exist but urgent action is needed,” Goldin added.

But the lack of a truly global response, particularly from the largest advertisers, has come under fire from campaigners and emboldened Facebook’s senior leadership. According to a report by the tech news site the Information, Zuckerberg sees the boycott as a PR issue rather than a serious threat and is not planning a major response.

“We’re not going to change our policies or approach on anything because of a threat to a small percent of our revenue, or to any percent of our revenue,” he said, according to the site. “My guess is that all these advertisers will be back on the platform soon enough.”

Advertisers needed to ensure their message was clear, Ahmed said. “If you’re a large company and you’re pulling your advertising from the US but not the rest of the world, that puts into question your commitment.

“It is by now clear that legislators are dithering around the world on taking robust legislative or regulatory action so it’s on the rest of us in civil society, which includes businesses, to send a clear message to social media companies.”

Ahmed’s call came after a group of 37 UK charities, including Barnardo’s, Mind and Parkinson’s UK, threatened to curb spending on social media engagement if platforms such as Facebook did not tackle hate speech.