Nearly half of Britons do not believe refugees should be welcomed into the UK, a YouGov survey found.
The survey also highlights an "extremely worrying" negative public attitude towards Muslims, Islamic Relief warned.
Some 42% said Britain should not take in foreign nationals fleeing conflict or persecution in their own countries, according to a poll of more than 6,000 people.
Meanwhile, 47% said the UK should not provide refuge to people fleeing Syria and other Middle Eastern countries
The charity Islamic Relief, which commissioned the research, said the results showed a "dramatic hardening of views" towards refugees.Just 31% of people believed the UK should not welcome refugees in a similar survey of 5,000 people last year, it said.
The findings come after Britain helped rescue more than 1,000 people off the coast of Libya this month, where hundreds are feared to have drowned so far this year trying to make the crossing to Europe.
The survey also revealed that the British public associate Muslims with terrorism more than any other issue.
"Extremist" and "misogynistic" were also phrases most likely to be linked to the religion by Britons, according to the poll.
The results of this poll are extremely worrying because they show that public attitudes towards Muslims are hugely negative and attitudes towards refugees have hardened significantly.
Researchers asked 6,640 people which three words or phrases they most associated with the term "Muslim".
12% said terror, terrorist or terrorism - the most frequently given phrase
11% said faith
9% said mosque
8% said Koran
8% said religious
5% of people said extremist or misogynist
5% said Allah, Mohammed and prayer
Muslim charities play a vital role in delivering aid to some of the world's most vulnerable people in some of the world's most dangerous places.
British Muslims donate more than £100 million to charity during Ramadan alone, and Islamic Relief's Ramadan Appeal raised a record £19 million last year - including a £5 million donation from the UK Government, according to the charity.