The broadcasting watchdog is investigating Channel 4 News for incorrectly saying that a radical preacher who is in prison was responsible for the Westminster terrorist attack.

Ofcom received 12 complaints about the blunder, which the news show had credited to an unnamed source.

The programme repeatedly said that the Westminster terrorist killer was Abu Izzadeen, during the broadcast on March 22.

Simon Israel, the programme's senior home affairs correspondent, later updated viewers, saying: "I appeared quite certain earlier in the programme but there appears to be some doubt now.

"A source was pretty certain that the attacker... was, as I earlier said, Abu Izzadeen... It now appears that that might not be the case.

"It might be someone else, owing to the fact that new information has emerged to suggest that Abu Izzadeen is still in prison."

Ofcom is investigating under rules on accuracy and the quick acknowledgement and correction of significant mistakes on air.

A spokesman for the watchdog said: "We're investigating this news item on the recent Westminster attack, which named the wrong person as being responsible."

The regulator is also investigating ITV News London, after receiving complaints about an interview with illustrator Tim King, which featured several of his drawings on-screen.

One picture about the Brexit referendum was shown for 14 seconds and included the text: "So who's voting in? Great because I'm calling it C***AGEDDON. I'm scared that the idiots could take over."

A spokeswoman said: "We are investigating this interview, which included comic book illustrations containing the most offensive language."