Former Treasury Secretary John B. Connally plans to create a political action committee to finance campaign, efforts he will make for congressional and gubernatorial candidates next year.

In doing so, Connally joins a growing number of possible Republican presidential candidates who either are considering or already have set up similar organizations to test the political waters and lay the foundation of a campaign committee for 1980.

They include Senate Minority Leader Howard H. Baker Jr. of Tennessee, former Republican National Chairman George Bush and Sen. Lowell E. Weicker of Connecticut.

Connally, in New Orleans for the Republican National Committee's semiannual conference last week, said he will not make a firm decision about the 1980 campaign until sometime in 1979.

He vigorously denied the political action committee effort for the 1978 congressional candidates would evolve into a personal campaign organization.

"My sole purpose next year is to try to elect more Republicans to Congress and to the statehouses," Connally said.

"IF we can't elect more than one-third of the U.S. House of Representatives we all ought to think about doing something drastic," he said.

Connally said the professional staff of eight to 10 he plans to assemble will be disbanded and replaced with a separate presidential campaign organization if he decides to run.

The staff will include advance personnel and speechwriters to arrange speaking tours across the country, Connally said.

After failing to generate much interest in his candidacy last year. Connally embarked on several ventures designed to sustain his visibility, including a "vital issues" policy research organization and a committee to raise money for congressional candidates.

Connally, 60, said his health, the feelings of his wife, Nellie, "plus about 1,000 other things" will be factors for him to consider before deciding to seek the nomination.

"I would have to feel I had a reasonable chance," the former Democratic Texas governor said.

Connally said postponing a decision until 1979 will allow him more freedom in addressing controversial issues, "I don't want to think like a candidate yet. When you start thinking like a candidate, you begin to trim your sails - that's not the role I want to play," he said.

In a wide-ranging discussion with reporters Thursday night, Connally showed little evidence of trimming any sails.

He proposed a national referendum to resolve the controversy over the Panama Canal treaties, and strongly condemned the "permanent bureaucracy" of Capitol Hill.

"The 17,000 congressional employees run this Congress and it's time to change all that," Connally siad. He proposed that representatives be limited to two four-year terms, and senators to one eight-year term. The President would be restricted to a single six-year term.