Retired chief justice Warren E. Burger yesterday defended Solicitor General Charles Fried and criticized a New Yorker magazine article that found Fried's staunch advocacy of the Reagan administration's ideological agenda has undermined the office's credibility with the Supreme Court.

The article, written by Lincoln Caplan, quotes seven current and two retired justices, all unnamed, as saying that under Fried there has been a "decline in the standing of the solicitor general" because the court believes the office is no longer politically independent.

Caplan, author of an upcoming book on the solicitor general's office called "The Tenth Justice," wrote that a majority of the justices felt "sadness and distress" about changes in the role of the office.

He said the others, including Burger, were "sometimes put off by Fried's advocacy." He quoted sources as saying that Burger believed Fried was "too willing to be a spokesman for the 'reactionary' Reagan administration."

Burger, in a letter to Fried dated Aug. 18 and released yesterday, said, "It has always been my view that the solicitor general is the government's advocate in the Supreme Court, not the Supreme Court's representative in the executive branch. Of course, judges expect high professional conduct from the solicitor general, and we have uniformly had just that.

"The tradition of the solicitor general's office has consistently been that of vigorous, candid, honest and honorable advocacy," Burger said.

Fried said last week that the New Yorker "piece is so one-sided and incomplete as to border on dishonesty."

Robert Gottlieb, editor of The New Yorker, yesterday defended the article, which was published in two parts earlier this month. "We have complete confidence in Lincoln Caplan and his sources," he said, adding that Burger has not complained to the magazine.

Sources familiar with the court yesterday backed up Caplan's asertion that Burger has criticized Fried's approach. They said, however, that Burger was "angered" that Caplan had quoted him as calling the Reagan administration "reactionary." They said Burger, a strong Reagan supporter, is unlikely to have used that term.

Caplan said in a telephone interview, "That word was reported to me by someone who worked closely with Chief Justice Burger at the court and who has proved to be reliable in the past . . . . "

He said he was told that Burger used the word "reactionary" in describing the Reagan administration during a discussion of the Bob Jones University case in which the administration sought to extend tax-exempt status to segregated schools. The court rejected the administration arguments in 1983 in an 8-to-1 decision written by Burger.

Burger also sharply criticized accounts of the Caplan article in The Washington Post and The New York Times.

In a brief written statement, Burger said the views attributed to him in the two newspapers "were flagrantly false and irresponsible, and I cannot understand why I was not called for verification since I was readily available by telephone, even though I was out of the city."

Burger was in San Francisco at the time, attending a meeting of the American Bar Association.