The British stars have signed up to a petition calling for Prime Minister David Cameron's government to implement legislation ensuring families fleeing persecution are protected.
Thompson, a patron of the Refugee Council, which is spearheading the campaign, acknowledges the issue is a cause close to her heart after she took in a 16-year-old Rwandan refugee in 2003.
She says, ""My son escaped violence in his country, and I am thankful every single day that he did. He was able to build a new life here - we have the UN Refugee Convention to thank for that. But it isn't easy and refugees still aren't treated with the dignity and respect they deserve.""