Ben Carson, the new Housing and Urban Development Secretary, has faced a backlash after referring to African-American slaves as 'immigrants'.

'There were other immigrants who came here in the bottom of slave ships, worked even longer, even harder for less,' Carson said in his first address to the agency's staff, according to the Washington Post.

'But they, too, had a dream that one day their sons, daughters, grandsons, granddaughters, great grandsons, great granddaughters might pursue prosperity and happiness in this land.'

Carson, who stood in the 2016 presidential primary before endorsing Trump, immediately attracted a backlash on Twitter, where he was top of the trending chart yesterday. The black pressure group the NAACP was among the critics.

Immigrants??? https://t.co/f0RH7iXBrn

— NAACP (@NAACP) March 6, 2017

The actress Whoopi Goldberg joined in the chorus of complaints, pointing out that while immigrants came to the country voluntarily, slaves were 'stolen'.

Ben Carson..please read or watch Roots, most immigrants come here VOLUNTARILY,cant't really say the same about the slaves..they were stolen — Whoopi Goldberg (@WhoopiGoldberg) March 6, 2017

This is not the first time that Carson, a former neurosurgeon, has made controversial comparisons to slavery.

During an interview with NBC in 2015, he compared it to abortion. 'During slavery — and I know that's one of those words you're not supposed to say, but I'm saying it — during slavery, a lot of the slave owners thought that they had the right to do whatever they wanted to the slave,' he said. 'What if the abolitionists had said, "I don't believe in slavery, I think it's wrong, but you guys do whatever you want to do"?'

At the Values Voter Summit in 2013, Carson called 'ObamaCare' the worst thing 'since slavery'.

'It is slavery in a way, because it is making all of us subservient to the government, and it was never about health care,' he said. 'It was about control.'