Three years after he launched himself on an unsuspecting American public as a prime-time interrogator of politicians and celebrities, Piers Morgan has admitted defeat in the nightly ratings battle and plans to step down from his CNN show.

The former tabloid editor, who has transformed himself into a cable news personality, said that dwindling viewing figures and an anti-gun campaign that alienated a vast swath of his audience had led him to conclude that his show had “run its course”.

“It’s been a painful period and lately we have taken a bath in the ratings,” he said. “I am a British guy debating American cultural issues, including guns, which has been very polarising, and there is no doubt that there are many in the