* Leaks included details of covert cyber attack on Iran
* News conference planned for Thursday
* McCain charges violations of law
By Susan Cornwell and Mark Hosenball
WASHINGTON, June 6 (Reuters) - The White House and a leading Republican senator accused each other of being "grossly irresponsible" on Wednesday in connection with a recent series of leaks of national security data.
White House spokesman Jay Carney denied allegations made by Senator John McCain a day earlier that the apparent leaks by administration officials must have been politically motivated to boost President Barack Obama's stature ahead of his attempted re-election this fall.
McCain fired back with a heated statement repeating his suspicions, declaring "this is not a game" and "laws have apparently been broken." He called for prosecution of whoever is responsible for the leaks, which have included information about a U.S. cyber warfare program aimed at thwarting Iran's nuclear program.
The tense sparring underscored how the handling of classified information and national security has suddenly escalated into a presidential campaign-season issue, like no time in recent memory.
Congressional intelligence chiefs also expressed deep unease about the recent leaks and said they would press the Obama administration to investigate, as well as considering how laws could be strengthened to stop it happening again.
"The accelerating pace of such disclosures, the sensitivity of the matters in question, and the harm caused to our national security interests is alarming and unacceptable," the leaders of the House and Senate intelligence committees from both political parties said in a statement.
"These disclosures have seriously interfered with ongoing intelligence programs and have put at jeopardy our intelligence capability to act in the future," the lawmakers said. The leaks put lives at risk, made assets harder to recruit and strained the trust of U.S. partners, they said.
The statement was signed by Senator Dianne Feinstein, Senator Saxby Chambliss, Representative Mike Rogers and Representative Dutch Ruppersberger. The group also announced a news conference on the subject for Thursday.
McCain, who challenged Obama in the 2008 presidential campaign, took to the Senate floor on Wednesday along with Chambliss to call for a special counsel to investigate the recent string of leaks, saying they appeared to have been made for political advantage.
The leaks have included detailed reports on a classified counterterrorism "kill list" of militants targeted in drone strikes, and an undercover investigation targeted on Yemen-based militants involved in building underwear bombs designed to foil airport security.
Carney, on Obama's plane on a flight to San Francisco on Wednesday, said the administration "takes all appropriate and necessary steps to prevent leaks of classified information or sensitive information that could risk ongoing counter terrorism or intelligence operations."
"Any suggestion that this administration has authorized intentional leaks of classified information for political gain is grossly irresponsible."
"No, what is grossly irresponsible is U.S. officials divulging some of the most highly classified programs involving the most important national security priorities facing our nation today," McCain shot back in his statement. (Editing by Cynthia Osterman)