Attorneys for Sen. Edward W. Brooke (R-Mass) deliberately stalled on handing oversome critical papers and allowed the alteration of others before they were given to the Senate Ethics Committee, the panel's former special counsel testified yesterday.

Over vehement objections from Brooke, whose finances are under investigation by the Ethics Committee and who is locked in a tight reelection race, Richard J. Wertheimer outlined his charges in a 54-page statement he summarized before a special hearing called by the committee at Brooke's request.

In addition to charging deliberate delay and "obliterations" in Brooke's financial records, Wertheimer told committee members yesterday:

That records obtained by the committee showed Brooke to have gotten $38,000 in loans from a Canadian businessman that were not reported on his Senate financial disclosure statements as required by law.

Changes in records turned over to the Ethics Committee's investigators altered the source of the money, Wertheimer said.

That Brooke swore falsely in June during a hearing in Massachusetts on his contested divorce that he concocted a story in 1977 about $49,000 he obtained. Wertheimer said documents held back by Brooke's lawyers show Brooke actually was using the phony story as far back as 1975 in his financial statements. Brooke has publicly s!apologized for the story, calling it a "misstatement."

That Brooke made false statements earlier this year to the press and Massachusetts regarding public-assistance Medicaid payments to his mother-in-law. Brooke said he did not know of the payments until they were reported in the press this year. However, Wertheimer said documents in Brooke's file going back to 1972 showed the existence of the payments and suggested Brooke's knowledge of them. The panel's former counsel said Brooke's attorneys at first denied that the documents existed.

That Brooke hid his full ownership of a land investmentcompany in St. Martin in the French West Indies since the company was formed in 1969. His interest in the company - called Remwin - was not reported on his Senate financial reports until this year when his Senate finance report - and his sworn financial statement filed in his divorce - showed a 39 percent stock ownership in the company. However, Wertheimer said Brooke's bank records show 100 percent ownership of Remqin and that the senator's attorneys failed to produce documents in the files about Brooke's stock in the company.

Wertheimer's statement is the most complete report thus far of the nearly four months of investigation the Senate committee has been conducting into Brooke's financial affairs.

Brooke opened yesterday's hearing with a strong denial tha he or his attorneys had hindered the ethics panel's investigation or altered any documents turned over.

Obviously caught by surprise and upset when a committee staff member began distributing Wertheimer's lengthy statement to the press, Brooke jumped to his feet to object.

"I just can't believe this is happening in this country, much less this committee," the 12-year Senate veteran told the hearing.

Brooke, who helped draw up the legislation creating the Ethics Committee, told its chairman, Sen. Adlai E. Stevenson (D-III), "I'd rather be before a grand jury or a court of law. My rights would be protected. I have no rights here."

Stevenson, obviously irritated by the vehemence of objections from Brooke and his attorneys, noted that Wertheimer's allegations did not deal directly with Brooke but did accuse his attorneys of withholding and altering evidence in the investigation.

Calling the hearing "a most regrettable experience," Stevenson noted that Brooke requested the session after Wertheimer resigned from the Ethics Committee staff Oct. 12, charging that Brooke's attorneys had held back and altered evidence required by investigators.

Stevenson acknowledged, however, that release of the Wertheimer statement to the press yesterday could have been a mistake. He allowed the hearing to continue today in order to give Brooke and Wertheimer a chance to make additional statements.

The committee voted in June to conduct what is formally called an "initial review." It is now looking into allegations of financial wrongdoing by Brooke and Sen. Herman E. Tanmadge (D-Ga). Stevenson said yesterday he hoped that the evidence concerning Brooke would "convince the public that our 'initial reviews' are unremitting and uncompromising."