LONDON -- More than four years after revelations of tabloid phone hacking shocked Britain, prosecutors said Friday that the criminal investigation is over, ruling out corporate prosecution of Rupert Murdoch's British newspapers or charges against individuals including former CNN host Piers Morgan.

Director of Public Prosecutions Alison Saunders said there was "insufficient evidence to provide a realistic prospect of a conviction" over corporate liability by Murdoch's News Group Newspapers.

She said 10 individuals under investigation at the rival Mirror Group -- including former Daily Mirror editor Morgan -- also will not face charges.

Morgan, who has been twice quizzed by police over claims he knew of illegal eavesdropping when he was editor between 1995 and 2004, tweeted that "I've never hacked a phone and nor have I ever told anybody to hack a phone."

"I'm now going to get spectacularly drunk," he added. "Happy Christmas."

Investigations into phone hacking, bribery and other forms of wrongdoing were triggered by the 2011 revelation that staff at Murdoch's scoop-hungry News of the World had eavesdropped on the voicemails of celebrities, politicians and even a missing teenage girl who was later found murdered.

Murdoch shut down the 168-year-old newspaper in July 2011 amid public uproar over the disclosures.

A huge police operation saw dozens of journalists and public officials arrested, though most were released or acquitted. Nine people have been convicted over phone hacking, including former News of the World editor Andy Coulson, who was also an aide to Prime Minister David Cameron.

Both Murdoch's News Corp. and Mirror Group Newspapers have admitted hacking and paid millions of pounds (dollars) in compensation to victims.

But the Crown Prosecution Service said Britain's law on corporate liability "makes it difficult to prove that a company is criminally liable if it benefits from the criminal activity of an employee, conducted during their employment."

It said that Coulson, the most senior figure convicted, "was not a controlling mind of the company" and "there is no evidence to suggest that any member of the board of NGN had knowledge of phone hacking when it was taking place."

Murdoch's British firm News U.K. said "the right decision has been taken."

"Long ago, we apologized for the conduct that occurred, immediately took steps to pay compensation to those affected, and updated and instituted substantial reforms in our business to ensure our governance is second to none," the company said in a statement.