Attorney General Eric H. Holder Jr. on Friday announced tighter controls over the ability of prosecutors to subpoena the phone and other records of journalists after criticism that the Justice Department’s aggressive pursuit of leak investigations was infringing on press freedom.

Under new guidelines, a reporter must be the target of a criminal investigation before Justice Department officials can obtain a search warrant for the journalist’s e-mails and other records.

News media organizations will also have to be notified if a reporter’s records are being subpoenaed, unless the attorney general decides it would harm a criminal investigation, according to a six-page report issued Friday and called “Review of News Media Policies.”

“The Department of Justice is firmly committed to ensuring our nation’s security, and protecting the American people, while at the same time safeguarding the freedom of the press,” said Holder in a statement. “These revised guidelines will help ensure the proper balance is struck when pursuing investigations into unauthorized disclosures.”

The guidelines, which will go into effect immediately, are the result of a backlash from the news media and press freedom organizations two months ago over a pair of newly disclosed leak investigations. In an unusually sweeping move, Justice officials obtained records from more than 20 phone lines assigned to the Associated Press and its journalists as part of a year-long investigation into the disclosure of classified information about a failed al-Qaeda plot last year.

The AP was not notified until 90 days later, which was permitted under existing guidelines. Gary B. Pruitt, AP president and chief executive. called the agency’s actions “a massive and unprecedented intrusion” into newsgathering activities.

Under the new guidelines, the Justice Department “will ensure notice in all but the most exceptional cases,” the report said. That action would allow news organizations to raise a legal challenge to the request.

If the attorney general decides such notice “would pose a clear and substantial threat to the integrity of the investigation, risk grave harm to national security, or present an imminent risk of death or serious bodily harm,” the department can delay notification for 45 days, according to the new guidelines.

At that point, the attorney general would again have to review his decision and may authorize a notification delay for up to an additional 45 days. No further delays can be sought beyond the 90-day period.

In a second leak investigation into former State Department arms expert Stephen Jin-Woo Kim, Fox News reporter James Rosen was called a possible “co-conspirator” in a crime in order to obtain a search warrant for his records.

The Privacy Protection Act of 1980 prohibits the search or seizure of work product and documentary material by individuals who disseminate information to the public. But an exception in that law allows such a seizure if there is “probable cause to believe that the person possessing such material has committed or is committing a criminal offense to which the materials relate.”

Under current Justice policy, a deputy assistant attorney general can authorize an application for such a search warrant and no higher-level review or approval is required. A Justice official said that would no longer be permitted.

A search warrant for a reporter’s records can now be obtained only if the reporter is the target of the leak investigation and not because he obtained classified information while reporting.

“It has been and remains the department’s policy that members of the news media will not be subject to prosecution based solely on newsgathering activities,” the Justice report said. “The department views the use of tools to seek evidence from or involving the news media as an extraordinary measure.”

The guidelines will also create a “News Media Review Committee” that will advise the attorney general and the deputy attorney general when Justice prosecutors request subpoenas or search warrants for information from members of the news media. The committee will include senior Justice officials, including the head of the department’s Public Affairs Office and its privacy and civil liberties officer.

Under the new rules, the department will begin releasing an annual list of the number of subpoenas and search warrants issued to reporters and news organizations. Justice officials said the Obama administration will continue to support efforts by Congress to pass a media shield law.

“While these reforms will make a meaningful difference, there are additional protections that only Congress can provide,” Holder said.

Media shield legislation, sponsored by Sen. Charles E. Schumer (D-N.Y.) would guard against some legal efforts to force journalists to divulge their confidential sources. It would require a judge, not the attorney general, to approve a subpoena for a reporter’s records.

In May, President Obama asked Holder to review the Justice Department’s guidelines for leak investigations and report back to him by Friday.

In the past two months, Holder has held seven meetings with about 30 news media organizations, including The Washington Post, as well as with First Amendment groups, media industry associations and academic experts.

Holder presented the new guidelines to Obama at the White House on Friday morning.