Reacting to sharp criticism on Capitol Hill, a Department of Energy official yesterday offered belated help in retrieving six copies of a secret document on the hydrogen bomb whose erroneous declassification in 1975 led to a security breach said to be the gravest in the history of the nuclear weapons development program.

Duane C. Sewell, DOE's assistant secretary for defense programs, volunteered the help to Dimitri A. Rotow, who made the copies more than two weeks ago after finding the document - known as UCRL 4725 - on the open shelves of DOE's library at the Los Alamos laboratory in New Mexico.

The help wasn't needed because, Rotow told a reporter, he already had called back the copies - hours after Sen. John Glenn (D-Ohio), at a Wednesday hearing of his subcommittee on nuclear proliferation, denounced DOE officials for having failed even to have asked Rotow for the names of the recipients.

"I just think that's incredible," Glenn said, "He had the H-bomb secret, we're worried about H-bomb secret going 'round the bloomin' world - and we don't even follow up to find out where the reports went."

In a related development, the American Civil Liberties Union launched a counter-attack against the publication restraint on The Progressive magazine with an announcement that it will request U.S. District Court Judge Robert W. Warren in Milwaukee to lift the preliminary injunction he issued, at the government's request, two months ago.

The ACLU said it will ask Warren to let it put into the record the erroneous declassification of UCRL 4725 and other new evidence that, it believes, weakens the government's case.

The new evidence includes Glenn's revelation that DOE discovered last summer, but had not disclosed, that it had declassified at least one other formerly secret document on thermo nuclear weapons, and 42 papers, found by Rotow on the open shelves at Los Alamos, that, he testified, are collectively more useful than UCRL 4725 to a putative H-bomb builder.

The ACLU made the annoucement after a conference in Chicago called by three judges of the 7th U.S. Circuit Court of Appeals, which is considering an ACLU petition to nullify Warren's order.

The ACLU's motion for opening the record to the new evidence will be filed within 30 days. The 7th Circuit has set Sept. 10 to hear argument on the appeal.