Chinese artist Ai Weiwei has urged the British government to do more to help refugees ahead of a landmark exhibition of his work.
He said he was "proud" of Germany for its response to the European migrant crisis and believes Britain should do more.
"It's a really urgent situation but not short-term, it's going to be lasting for a very long time and takes global effort from different nations," he said.
"I think the Western countries have to come up with some sort of decision to help each other and get a better, more sound way to deal with the situation."
He added that Germany had acted in a "very civilised way" by "opening its arms" to many refugees.
"I believe British people also have very strong compassion and I think the Government should take a better position on that," he said.
Ai travelled to London for the first time in five years for his upcoming exhibition at the Royal Academy of Arts after his passport was confiscated by Chinese authorities.
He said his incarceration in China had "deeply affected" him and his family, especially his six-year-old son.
"He had nightmares that they would never let me out," he said. "We used to FaceTime but he often lost face.
"My mum got older so fast."
The Home Office previously apologised to Ai after initially refusing him a visa to travel to London for his exhibition. He was later issued a full six-month visa.
His exhibition will open to the public on September 19.
Tim Marlow, artistic director at the Royal Academy, said: "There was an incident, a cock-up more than a conspiracy, you weren't given a visa from the British Embassy, after being given your passport back you weren't given a visa."
Ai replied that he turned to social media as a last resort after trying to convince the British authorities he did not have a criminal conviction.
"I tried to explain, I feel very funny because obviously this is a wrong excuse," he added.
"I'm very happy they changed it very fast and admire the way you can change a very formal decision so fast."
He said he "really appreciates" the outpouring of support he received online.
Ai spent 81 days in prison in China for alleged "subversion" offences but was never charged.
"They said I had too much foreign supporters and talk to too many journalists, that was the reason," he added.
He said when his passport was finally handed back there were no conditions attached but added he has "no idea" what will happen when he tries to return to China in two weeks.
"Still in China I have to work very carefully if I want my work to be showing," he added.
"I have to be very careful, there's always censorship there, unless you don't care and don't want to show it there."