The actor Benedict Cumberbatch has shown his growing frustration over the migration crisis during a speech after his Hamlet performance – reportedly saying “fuck the politicians”.

The Sherlock star has been giving nightly speeches after his curtain call at the Barbican in London and asking for donations to help Syrian refugees. So far, audience contributions have raised more than £150,000 for Save the Children.

Cumberbatch has been particularly critical of the British government’s decision to accept only 20,000 refugees over five years.

During the speeches, Cumberbatch has been reading a poem called Home by Somali poet Warsan Shire, the same one he read in the introduction to Help is Coming, Save the Children’s charity single, released in the summer. It includes the line: “No one puts children in a boat unless the water is safer than the land.”

Cumberbatch has told theatregoers of a friend’s experience volunteering on the Greek island of Lesbos, where 5,000 people had been arriving every day.

“Everywhere on the horizon there was nothing but boats and on the shoreline nothing but lifejackets,” he said. “We are saying, as citizens of the world, we see you … and at least some help is coming.”

Several members of the audience on Tuesday said they supported Cumberbatch’s frustration with politicians, which led him to use the swear word.

Benedict Cumberbatch after Hamlet RE the refugee crisis: 'Fuck the politicians" — Ellen (@Needforcaffeine) October 27, 2015

"Fuck the politicians" - Benedict Cumberbatch, at bows for Hamlet — gav gav galloo (@govieburbie) October 27, 2015

“Out of nowhere came this ‘Fuck the politicians’ remark,” one theatregoer told the Daily Mail. “It’s not quite what you’d expect when you go for an evening with the bard, but it got a few cheers.”

Cumberbatch has previously expressed a desire to meet the home secretary to discuss the refugee crisis. “I don’t think the government is doing enough, I’m glad to say that,” he told Sky News at the premiere of his new film, Black Mass, this month. “I would like to sit down with Theresa May and really get an idea of how her economic and political model works.

“There is a huge crisis and not enough is being done. Yes, we need long-term solutions; yes, we need to get people out of the camps so they don’t make a perilous journey; yes, it’s a good idea to actually have a specific solution, I suppose, once they arrive here. But to say 20,000 over five years when 5,000 arrive in one day? We’ve all got to wake up to this.”

• This article was amended on 30 October 2015. An earlier version said the Lib Dem peer Shirley Williams was in the audience for Hamlet on Tuesday, and included an embedded tweet from someone who had said Lady Williams was there. Williams’ office has been in touch to say she was not in the audience for Hamlet, and had been at the Barbican that day for a different event, a recital by the pianist Stephen Hough. Nevertheless, she completely agrees that the UK government needs to do more to help refugees from the Syrian crisis.

