Game of Thrones actor Lena Headey, who is starring in one of the first British films to grapple with the refugee crisis, has spoken out against the “horrendous and dehumanising” way that people seeking safety in the UK are treated.

The Flood sees Headey play British immigration officer Wendy, who is presiding over the fate of Eritrean refugee Haile, whose journey escaping from the war-torn African country to the Calais camp and eventually to England is traced in the film.

Headey, best known as Cersei Lannister in Game of Thrones, said having been put in the shoes of an immigration officer and exposed to a script based on real-life accounts from people working for the Home Office had affirmed her belief that a shift in attitude was needed.

“I understand there are safety issues, and screenings for security, but it could be so much more human and compassionate,” said Heady. “It’s horrendous that after the journeys that these refugees go through, they are then treated immediately with suspicion and fear.

Headey plays Cersei Lannister in Game of Thrones. Photograph: AP

“I get it, this is a crisis with so many levels, but we have also lost sight of the fact it’s not a ‘problem’, it’s people, it’s other human beings. And we’re dehumanising them.”

While there have been several critically acclaimed documentaries that have followed the plights of the hundreds of thousands fleeing the Middle East and Africa, barely any feature films on the issue have made it into production.

Headey said she noted how in the wake of events such as Brexit, conversations about the refugee crisis had begun to dwindle, and said that had been a motivating factor in her getting involved in the film. Written by Helen Kingston, the film was initially inspired by an incident in which 35 immigrants from Afghanistan were discovered in a shipping container at Tilbury Docks in Essex in 2014, with some dying during the ordeal.

“The power of film to change people’s minds is a real thing,” she said. “I, Daniel Blake was a really good example of this, it woke people up – it woke me up – to the injustice of something that is happening now, right under our noses. This film is about the horrors of what is happening every day to the refugees coming to Europe, and how appalling and frightening it is to sit by while it goes on.”

She added: “I hope it will provoke similar kinds of conversations. It’s amazing how quickly it seems to have died down even though it’s as a bad as it ever was.”

Headey said she fully understood people’s fatigue having been bombarded with images of violence and human suffering every day, but said she believed the most important task was to make people less fearful of the refugees and their motives for coming to the UK. Having visited Greece last year to meet some of those who had made the perilous journey across the Mediterranean, Headey said she had been struck by how the main message the women wanted to convey was that “we are not terrorists”.

Yet she also noted what she described as a “massive discontentment” among the men living in the makeshift camp on the island of Lesbos.

“If we don’t have a shift where we recognise these people for who they were before they were forced to leave their countries – people who are educated with family values, who had careers and homes – then we are going to be in trouble, we really are. We are going to grow an absolute fury, you could feel it.”

With the next season of Game of Thrones premiering in July keeping Headey firmly in the limelight, she said she had come to accept that publicly speaking out about the refugee crisis would prompt a backlash.

“People look at actors who speak out and say ‘oh well, it’s so easy for them’,” she said. “There are a lot of people who are saying ‘it’s all right for you, you champagne socialist’ but that’s fucking bollocks, I’m just a human being with a conscience.

“My kids need to know that I gave a shit – that’s what drives me most,” Headey added. “I’m a jobbing actor, this is what I do to make cash, but sometimes I do projects where I make no cash because it’s about making something that will hopefully get people talking.”