Channel 4 News has apologised after its presenter Jon Snow said he had “never seen so many white people in one place”, referring to the pro-Brexit protesters who flooded the centre of London on Friday.

The 71-year-old frontman was broadcasting live from outside the Houses of Parliament when he made the unscripted remarks while wrapping up the programme.

Snow said: “It’s been the most extraordinary day. A day which has seen … I have never seen so many white people in one place, it’s an extraordinary story. There are people everywhere, there are crowds everywhere.”

The remarks drew criticism online from some viewers who described Snow’s comments as unnecessary.

In a statement, Channel 4 said: “This was an unscripted observation at the very end of a long week of fast-moving Brexit developments.

“Jon has covered major events such as this over a long career and this was a spontaneous comment reflecting his observation that in a London demonstration of that size, ethnic minorities seemed to be significantly under-represented. We regret any offence caused by his comment.”

The broadcasting regulator Ofcom said that it would not know until Monday how many complaints had been made about the incident. A spokesman said: “We will assess any complaints we do receive before deciding whether or not to investigate.”