Richard Dawkins has slammed the Republican primary candidates for their belief in creationism and labelled Ben Carson a "disgrace."

The British evolutionary biologist spoke to CNN's Fareed Zakaria and said he found the candidates' reluctance to accept evolution "deeply depressing". All of the Republican presidential candidates apart from Trump have said they do not believe in evolution.

"This is not something you believe in or not," said Dawkins.

"I mean, this is a fact. It is a fact. It's just as much of a fact as the Earth goes around the Sun. You can't not believe it unless you're ignorant."

However Dawkins said he did not think the candidates actually believe creationism but thought they needed to say that in order to appeal to Republican core voters.

"I believe what they're doing is they think that they've got to say that in order to appeal to their constituency," he said. "And if that's true, it's deeply depressing."

Ben Carson, who is currently enjoying a surge in the polls, was the recipient of Dawkins' most stinging attacks.

"You just told me all the Republican candidates except one don't believe in evolution," said Dawkins. "I mean, that's a disgrace.

"But for a very senior eminent distinguished doctor as he [Carson] is to say that is even worse. Because of course, evolution is the bedrock of biology and biology is the bedrock of medicine. He clearly doesn't understand the fundamental theorem of his own subject. That is a terrible indictment.

"It is a form of arrogance to say we know what God does," Dawkins continued. "The only way to know anything is by looking at the evidence. In this particular case, the evidence is overwhelming... In the case of evolution, there is no doubt. It is a fact."

Carson is an outspoken Christian whose rise in popularity has placed him second to Donald Trump in the polls. However the former neurosurgeon has drawn criticism for previously saying the theory of evolution was created by the Devil and that the big-bang theory is "ridiculous" and a "fairytale."