“After a thorough analysis, we have decided there is insufficient evidence to provide a realistic prospect of a conviction and therefore no further action will be taken in any of these cases,” Alison Saunders, director of public prosecutions, said in a statement. “These decisions bring the C.P.S.’s involvement in current investigations into phone hacking to a close.”

Image Rupert Murdoch in 2011. Credit... Sang Tan/Associated Press

The investigation convulsed the news establishment and the political elite, and prompted a reckoning within the close-knit world of the British news media: Journalists were found to have illegally listened to voice mail messages and bribed police officers, and were said to have hired private investigators for illegal surveillance and information gathering.

Piers Morgan, the former editor of The Daily Mirror, wrote on Twitter that he had been informed by prosecutors that no further action would be taken against him as part of the phone-hacking investigation.

“As I’ve said since the investigation began four years ago, I’ve never hacked a phone and nor have I ever told anybody to hack a phone,” Mr. Morgan, who hosted a talk show on CNN for four years, wrote on Twitter. “Thanks to all my family and friends, and kind people on here, for all their support. It was greatly appreciated.”

In July 2011, Mr. Murdoch’s newspaper holding company in Britain, then called News International, closed the tabloid News of the World after it emerged that a private investigator employed by the Sunday newspaper had intercepted voice mail messages left on the cellphone of a kidnapped teenager in 2002. The teenager, Milly Dowler, was later found dead.