A high-level Defense Department official said that the Reagan administration is likely to seek legislation to stiffen penalties against government officials who disclose secrets to the press.

The legislation would be part of a general offensive against unauthorized leaks during the president's second term.

Fred C. Ikle, undersecretary of defense for policy, told a conference of reporters and government officials here Friday that the government "needs stronger laws to deter people who are about to be careless."

"The laws are not adequate," he said, and "we have decided to fight it on all fronts."

Administration officials have complained frequently that national security and diplomacy are harmed by the unauthorized disclosure of government secrets. During President Reagan's first term, Congress blocked several administration initiatives aimed at discouraging leaks, including regulations mandating wider use of secrecy pledges and lie-detector tests.

Reporters have countered that most leaks come from senior officials and reflect internal policy disputes, but do not endanger national security.

After his remarks Friday evening, Ikle told reporters that he does not necessarily have specific legislation in mind. He said it may be more important to seek "the moral support" of Congress in preventing leaks and to seek greater discipline in the executive branch.

"This is Justice Department business," he said. "I don't want to speak for them."

But Ikle also said that the 30-year-old Atomic Energy Act, which provides strict penalites for willful disclosure of information about nuclear weapons, should be extended to other technologies. He said he favors "cleaner laws, not sweeping, just somewhat cleaned up."

Fred W. Friendly, organizer of the conference here on "the military and the news media" and a professor at the Columbia University Graduate School of Journalism, responded by jokingly giving Ikle a copy of the Constitution.

"If you're worried about these links, hire people who believe in what you are doing," Friendly said.

Ikle acknowledged that previous administrations also have declared war on leaks, with limited success. But he said this effort may be more successful.

"We have determined not to give up," he said. "Because if we fail, we will be wasting hundreds of millions of dollars or endangering thousands or millions of lives."

Ikle did not cite any examples of disclosures that had cost lives in the past, but he said he was referring to "serious, hard-core leaks" that could endanger lives in the future. He cited disclosure of sources and methods of intelligence collection, information about "stealth" technology that the Pentagon is developing to help bombers fool enemy radars, operational details about U.S. military movements and collection of information about terrorists abroad.

But Ikle said he does not favor cracking down on what he called "soft-core" leaks about internal policy disputes, personnel changes or waste in government management.