A public interest defence should be introduced to protect journalists from legal action, former top prosecutor Sir Keir Starmer said.
The shadow Brexit Secretary said changing the law would allow cases to be filtered out before they reached a jury.
But the ex-Director of Public Prosecutions (DPP) refused to apologise to the string of journalists from The Sun who were pursued through the courts but were acquitted of wrongdoing.
At an event in Westminster, he said a general defence would be "very helpful".
He told the Parliamentary Press Gallery: "If you adopt the proposition that every time a prosecution fails, there has got to be an apology from the prosecutor, you get into very, very dangerous territory.
"Never forget those that are serving time for Stephen Lawrence's murder now were once acquitted and, therefore, would have had an apology on that analysis."
The multimillion-pound Operation Elveden, which the Metropolitan Police launched in 2011 to investigate payments by reporters to public officials, cost £14.7 million and led to 90 arrests and 34 convictions, including police officers and 21 public officials.
In the 29 cases against journalists, they were either cleared by juries, the charges against them dropped, or their convictions quashed.
Sir Keir said: "They were a difficult set of decisions. I think, in fairness, some of the measures taken by The Sun itself in relation to some of the journalists was based on the proposition there was something there that needed to be dealt with.
"The question is was the decision to prosecute taken in the right way, according to the right test? And the answer is, when I was DPP, yes. I'm sure when I wasn't DPP, yes."
Sir Keir said reforms would help police and prosecutors as well as journalists.
"I was concerned at the time and I remain concerned now that there isn't a public interest defence available for journalists," he said.
"I think this is a problem where journalists in the course of their business necessarily have to rub up against difficult rules.
"Some of them have a public interest defence and some of them don't and that's not satisfactory.
"I think it would be helpful for journalists. It would be helpful for the police and it would be helpful for prosecutors if there was a public interest defence up front because I think, if anything, what those cases showed me was if you test the public interest only when you get before the jury, and there's no way of effectively filtering it out beforehand, you run the risk of these sorts of cases."