After 15 months of deliberation, the Senate Select Committee on Ethics voted unanimously yesterday to denounce Sen. Herman E. Talmadge (D-Ga.) and recommended that he repay nearly $13,000 in improper expense funds channeled into a secret bank account.

In a strongly worded resolution read out by a grim-faced Sen. Adlai E. Stevenson (D-Ill.), the committee chairman, the six-member panel accused Talmadge of "gross neglect of his duty." The committee's resolution called Talmadge's financial conduct "reprehensible" and said it brought "dishonor and disrepute" to the Senate.

Talmadege, a 23-year Senate veteran who already is running for re-election next year, quickly labeled the committee's decision "a personal victory."

"There is no finding of intentional wrongdoing. There is no recommendation of censure," said Talmadge.

Historically, censure would have been the strongest measure that the committee could have recommended that the Senate take against Talmadge. Only seven members of the Senate have ever been censured.

The ethics panel's resolution yesterday sets up the final step in the complex procedure that the Senate uses in cases against one of its members. The resolution is expected to go to the Senate floor for a vote after the ethics committee releases its full report on the Talmadge case.

A committee spokeswoman estimated yesterday that the full report should be completed in about two weeks.

Talmadge declined yesterday to say whether he plans to fight the committee's action when it goes to the Senate floor. The Georgia senator, who is chairman of the Senate Agriculture Committee and is one of the Senate's most powerful members, has been quietly lining up support from other southern Democrats in case he chooses to contest the resolution that he be "hereby denounced."

If the full Senate approves the resolution and chastises Talmadge, he would be the first senator to have disciplinary action taken against him by the Senate since the late Thomas Dodd (D-Conn.) was censured in 1967.

In its resolution yesterday, the ethics committee said Talmadge had failed to sign and supervise 15 office expense vouchers for false expenses that were submitted to the Senate between 1973 and 1977. Talmadge already has voluntarily paid back $37,125 that was improperly vouchered, claiming it was an office bookkeeping mistake.

In addition to asking that Talmadge be ordered to pay interest on that money, the ethics committee also called on the Senate to require Talmadge to repay an additional $12,894 for other excessive reimbursements to his office.

Stevenson told reporters yesterday that the $12,894 covered two vouchers submitted by Talmadge's office that eventually went into a secret account in the Riggs National Bank here. The account was set up in 1973 by Talmadge's former chief aid Daniel Minchew, who told the ethics panel earlier this year he opened the account with Talmadge's knowledge and consent.

The committee also charged that Talmadge failed to report more than $10,000 in campaign contributions between July 3, 1973, and Nov. 29, 1974, as required by law. That money also went into the secret account, the committee resolution said.

The resolution also said Talmadge failed to file Senate financial disclosure reports from 1972 to 1977 and failed to file his 1973 campaign financial report on time. The committee said he filed inaccurate campaign reports twice in 1974.

The committee said that certain disclosures made in the course of the Talmadge case could constitute violations of law if they are true. While not specifying what evidence it had in mind, the panel said it will make its files available to the Justice Department for possible further criminal action.

Although the whole committee avoided the word "censure" in its resolution, two committee members, vice chairman Sen. Harrison Schmitt (R-N.M.) and Sen. Mark Hatfield (R-Ore.) said they believe the terms used in the document constitute equally strong disapproval.

The committee had been wrestling with what kind of semantic stance to take. Talmadge indicated at the start of the proceedings that he would accept the word "reprimand," but Stevenson and Schmitt refused to accept that because they said it was too mild to cover the charges against Talmadge.

A compromise was proposed using the word "condemn" but Talmadge's advisers indicated they did not like that word either. The only member ever condemned by the Senate was the late Joseph McCarthy (R-Wis.) but Senate records were later changed to reflect the action as a censure.

Hatfield said the committee turned to a dictionary and thesaurus yesterday to arrive at its final charge that Talmadge "is hereby denounced."

Webster's dictionary defines "censure" as: "to blame; condemn as wrong". It defines "denounce" as: "to condemn strongly."

Committee members said they voted down a resolution by Schmitt to censure Talmadge during the panel's closed session yesterday 5 to 1.

Noting that the committee has been divided all along on the Talmadge case, Hatfield said later, "It would have been a hell of a thing if we weren't unanimous and ended up debating ourselves on the Senate floor. So we created a new word to express our feelings."

Stevenson said the committee also decided not to recommend that Talmadge be stripped of his powerful committee posts because he said "in addition to disciplining the senator, it would have been punishing his constituents."

Talmadge said he does not believe the committee's action would affect his reelection chances. "The ultimate ethics committee," he said, "are the people of Georgia."