On Friday it was revealed that the CNN host and former editor of the Daily Mirror newspaper, Piers Morgan, had been interviewed under caution by police investigating phone hacking. Officers from Operation Golding will have wanted to talk to Morgan about his now infamous claim that “I have never hacked a phone, told anyone to hack a phone, or published any stories based on the hacking of a phone.”

That categorical denial looks increasingly implausible when you look a the volume of evidence against him. Before the phone hacking scandal blew up in 2011, Morgan had – somewhat foolishly on his part – repeatedly explained in detail how voicemail intercepts were commonplace among London newspapers.

Regarding a story about Paul McCartney and Heather Mills the Mirror ran while he was editor, Morgan admitted, “At one stage I was played a tape of a message Paul had left for Heather on her mobile phone.” When asked under oath during the Leveson Inquiry into press ethics how his paper had obtained the message, he refused to answer.

In his 2009 diaries Morgan described how he broke the story of an affair involving England football manager Sven-Goran Eriksson: “It was the Daily Mirror, under my editorship, which exposed Sven’s fling with Ulrika Jonsson after learning of a similar message left by the then England manager on her phone.” And it was in his diaries that Morgan confessed his knowledge of how to hack phones: “If you don’t change the standard security code that every phone comes with, then anyone can call your number and, if you don’t answer, tap in the standard four digit code to hear all your messages.”

Writing in GQ magazine, Morgan again explained the method and played down the the consequences: “Reporters could ring your mobile, tap in a standard factory setting number and hear your messages. That is not, to me, as serious as planting a bug in someone’s house.” He may have not thought it serious then, but the crime of intercepting voicemail communications carries a possible two-year prison sentence.

If the evidence from Morgan’s own mouth is enough to raise considerable suspicion, the testimony of his peers is even more damning. Morgan was editor of the Mirror from 1995 to 2004, and it was during his tenure that former Mirror journalist James Hipwell alleged, “Many of the Daily Mirror‘s stories would come from hacking into a celebrity’s voicemail… I used to see it going on around me all the time when I worked at the Mirror.”

The BBC journalist Jeremy Paxman recalls how at a lunch in 2002, “Mr. Morgan was teasing Ulrika that he knew what had happened in a conversation between her and Sven-Goran Eriksson… He turned to me and said, ‘Have you got a mobile phone?’ “I said ‘Yes,’ and he asked if there was a security setting on the message bit of it. I didn’t know what he was talking about.”

In December, giving evidence at the hacking trial of former newspaper editors Rebekah Brooks and Andy Coulson, legal adviser Ambi Sitham alleged that Morgan once boasted to Brooks, “I know what your splash is because I’ve been listening to your messages.” Brooks replied, “Been hacking into my phone again have you, Piers?”

Morgan was also singled out for heavy criticism by the judge in charge of the Leveson Inquiry, Lord Justice Brian Leveson. Commenting on his evidence, Leveson concluded that “Mr. Morgan chose his words very carefully when asked to speak about the Daily Mirror.” Of one of Morgan’s replies to a question on hacking, Leveson warned, “This was not, in any sense at all, a convincing answer,” and summing up his testimony overall, described it as “utterly unpersuasive.”

So far the hacking trial has focused primarily on activity at the News of the World newspaper, though evidence at the Brooks-Coulson trial has also implicated Mirror Group newspapers in alleged criminality. Operation Golding, the investigation into behaviour at Mirror Group newspapers, is far less advanced than the Operation Weeting investigation into News of the World, and is still in the process of collecting evidence.

However, one Sunday Mirror journalist has already pleaded guilty to phone hacking. It may not be long before CNN are forced to make a difficult decision about the employment of their star host.