Suffolk County District Attorney Garrett Byrne yesterday announced his decision that there is insufficient evidence to pursue perjury charges against embattled Sen. Edward W. Brooke (R-Mass.).

He acted on the recommendation of a special prosecutor who had been named to investigate Brooke's admitted lies under oath during his divorce case.

Former Supreme Judicial Court justice Jacob J. Spiegel, appointed by Byrne July 12 to probe the matter, advised in a 33-page report that Brooke does not appear guilty of "materially misrepresenting" his finances. "Material misrepresentation," legally, only would have occurred if Brooke's lie inflating his liabilities had affected the outcome of the property settlement.

Under Massachusetts perjury law, Brooke could not be convicted just for his false testimony on a May 12, 1977, court depotiion. He woul also have had to deceive his estranged wife intentionally into accepting a smaller divorce settlement as a result of his admitted "misstatement."

"I have maintained from the beginning, as you know, I had no intention to deceive my wife or anyone else in the settlement of my divorce." Brooke said in a news conference yesterday, as aides beamed around him.

"This is a day we've all been waiting for," said Brooke's press secretary, Robert Waite, as he shook hands with a smiling administrative assistant just before the senator arrived here from Washington.

Brooke told reporters that he was pleased with the district attorney's decision adding, "Hopefully, this clears this matter," an apparent reference to the multitude of legal and political problems stemming from the divorce that Brooke has faced over the past few months.

Brooke still faces an investigation into his tangled finances by the Senate Ethics Committee.

Brooke's attorney, Charles Morin, complained Monday that the Ethics Committee's injury into his client's financil affairs was too broad.

The nation's only black senator two weeks ago saved himself from a potentially disastrous second divorce trial during his campaign for a third term when he agreed to a substantially larger settlement for his wife, Remigia, a move ending his 31-year marriage.

The divorce case had been reopened by Middlesex County Probate Judge Lawrence T. Perera because of Brooke's admitted misstatements about a $49,000 personal loan.

He testified the loan came from a friend, Massachusetts liquor distributor A. Raymond Tye. It was later revealed that $2,000 came from Tye and the remainder was money he was holding for his late mother-in-law.

In his report to Byrne, Judge Spiegel, a widely respected jurist noted as the presiding federal court appointed master in the Boston desegregation case, stated that Brooke's liability to his mother-in-law's estate as of March 11, 1977, was not $47,000 but $37,716. Therefore, he said, Brooke overstated his liabilities by only $9,283, representing less than 4 percent of his total liabilities.

"It is difficult to conclude that this overstatement . . . would have had a tendency to affect, to a reasonable degree, financial settlement of the parties' domestic difficulties," Spiegel wrote in his recommendation against prosecuting Brooke for perjury.

Working with a certified public accountant and two research assistants, Spiegel conducted an intensive two-week investigation of Brooke's finances, interviewing several witnesses and reviewing hundreds of pages of court testimony and evidences, before filing his recommendations.

Staring into the television cameras yesterday, Brooke told viewers, "I want to thank the public and my friends for their faith and confidence in me during this long period of travail."