Several hundred of the nation's business and financial leaders are preparing a massive publicity campaign this month calling for drastic changes in President Reagan's budget and tax policies to reduce federal deficits projected by the administration.

A draft advertisement being circulated among the businessmen, financiers, lawyers and academics says that "The federal budget is now out of control . . . . This fiscal course is senseless."

The advertisement, drafted by financier Peter G. Peterson, commerce secretary in the Nixon administration, calls for big cuts in defense and Social Security spending, and increased taxes that, it says, would "require tangible sacrifices from many middle and upper income citizens."

Called a "bipartisan appeal" to Reagan and Congress, it is an attack on Reagan's commitment to a sharp defense buildup and his unwillingness to raise taxes.

The draft ad warns that without these measures the economy may continue "stagnating for the remainder of the century," as large budget deficits keep interest rates high. "Tomorrow's big deficits . . . are already doing serious damage now and will wreak even more havoc in the coming decade and beyond," the draft says.

Peterson said yesterday that the advertisement has not been approved by those whose signatures appear on it, and he expects some changes before it is run later this month in The Washington Post, The New York Times and The Wall Street Journal.

If printed substantially in its present form, it would be an unusual and major break with the administration by top business leadership.

Edward G. Jefferson, chairman of E.I. duPont de Nemours & Co. Inc., one of the potential signers, said yesterday that the advertisement is "nothing but a draft" and that he was "distressed" that it had been released. He would not comment on the contents, but said "the purpose of Peterson's group . . . is to get a cohesive bipartisan approach to this problem" of high interest rates and high unemployment.

The White House has received a copy of the proposed ad but has no comment, White House spokesman Larry Speakes said yesterday.

Among the recommendations that the advertisement will make, Peterson said, are:

Major cuts in Social Security, federal retirement pay and other social programs that are not based directly on need. Benefits in these entitlement programs should be frozen temporarily and automatic cost-of-living adjustments capped, Peterson said. The draft advertisement calls for about $60 billion of savings in these programs by 1985.

A $25 billion reduction in defense spending by 1985, on top of the proposed caps on military retirement pay.

Increased taxes on consumption. The draft advertisement calls for about $60 billion in new taxes in 1985, including high energy taxes and higher excise taxes, such as on alcohol and tobacco, and additional user fees for government services.

The principles of the program, Peterson said, are fairness, stimulating investment, and focusing attention on future deficits.

He and other founding members of the bipartisan appeal held a news conference in May calling for some of the same objectives, although with less detail.

The five founding members, other than Peterson, all were former treasury secretaries. They included W. Michael Blumenthal, President Carter's treasury secretary; John B. Connally, treasury secretary under President Nixon; William E. Simon, at Treasury under President Ford; C. Douglas Dillon, treasury secretary under Presidents Kennedy and Johnson, and Henry H. Fowler, also treasury secretary for Johnson.

However, since then the group has assembled hundreds of corporate leaders to its cause. The potential signers of the economic manifesto listed on the draft are an all-star cast from big business and finance, the academic world and law firms.

It includes Samuel H. Armacost, president of Bank of America; Alton W. Whitehouse Jr., chairman of Standard Oil Co. of Ohio; James D. Robinson III, chairman of American Express Co.; Donald Kennedy, president of Stanford University, and Lee Iacocca, chairman of Chrysler.

Several of the persons listed as signers confirmed that they had authorized the use of their names, but not all had seen the text or endorsed its specific proposals.

Among those who confirmed that they had signed the advertisement were J. Richard Munro, president of Time Inc.; Lewis W. Lehr, chairman of Minnesota Mining and Manufacturing Co.; John G. Breen, chairman of the Sherwin-Williams Co.; D.L. Commons, president of Natomas Co.; Norman Hackerman, president of Rice University in Houston; Arthur Levitt Jr., chairman of the American Stock Exchange, and Thornton F. Bradshaw, chairman of RCA Corp.

"I recognize that it's strong medicine, but we have strong problems," Hackerman said.

Some of the listed signers apparently were surprised to hear that a text was being circulated, although none of those contacted by The Post denied authorizing the use of his or her name. A few, such as Stanley L. Temko, managing partner of the law firm Covington & Burling, and Robert H.B. Baldwin, president of Morgan Stanley and Co. investment bankers, referred all questions to Peterson.