19:50

Andrew Sabisky has stepped down as an adviser to the prime minister amid intense scrutiny over his views on eugenics and other issues.

Andrew Sabisky (@AndrewSabisky) I know this will disappoint a lot of ppl but I signed up to do real work, not be in the middle of a giant character assassination: if I can't do the work properly there's no point, & I have a lot of other things to do w/ my life

Boris Johnson’s spokesman had earlier refused to say whether or not the prime minister agreed black people had lower IQs on average or that benefit claimants should be encouraged to have fewer children than people in work – all among the views expressed by Sabisky.

Labour had called on No 10 to sack Sabisky, who was believed to have been contracted by Downing Street under Johnson’s de facto chief of staff, Dominic Cummings, to work on special projects.