The chairman of the House government information subcommittee announced yesterday that the Reagan administration had refused to send any witnesses to explain a proposed new secrecy order under consideration at the White House.

Rep. Glenn English (D-Okla.), the subcommittee chairman, called the decision "unfortunate" in light of the "many unanswered questions about the intent of the administration" in drafting the new rules for classifying government documents.

English canceled a hearing he had scheduled for Thursday to review the proposal with government witnesses. The subcommittee will proceed as scheduled today with testimony from journalistic, scholarly and other outside groups, most of which are expected to be critical of the order.

The administration's position on the hearing contrasts sharply with the approach President Carter took in 1978 when the current rules were promulgated. Copies of the Carter draft were circulated widely, public comments were accepted and considered, and the Justice Department provided testimony on the work in progress.

The Reagan administration proposal would make it easier to classify government documents secret and harder to get them declassified.

Attorney General William French Smith and President Reagan's special assistant for national security affairs, William P. Clark, were asked to send representatives to explain the proposed new rules. Both men declined.

Assistant Attorney General Robert A. McConnell informed English by letter that the Justice Department thought it "inappropriate" to send anyone, because "the process of revising the executive order has not been completed and the matter has not yet been presented to the president for decision."

The National Security Council's staff secretary, Michael Wheeler, asserted in a separate note that copies of the Reagan White House draft had been provided to selected congressional committees with "the explicit understanding that administration witnesses would not appear at hearings while the internal deliberative process was under way." English said that he had no such understanding.

English said the draft order, which can be issued without congressional review or consent, is "so broad and vague that it might even permit the classification of road maps of the interstate highway system."

He was alluding to a provision in the draft order setting down "the vulnerabilities or capabilities of systems, installations or plans relating to the national security" as a new category for classification.

"It's easy to imagine extremes when you can fit that kind of example about interstate road maps into the language they've used," English said. "Either they want an awful lot of flexibility or they did an awfully sloppy job in the first place. We'd like to find out which it is."

Both the Justice Department and NSC offered in their letters to answer questions from members of English's subcommittee on "an informal, consultative" basis, but English said he saw no reason for balking at a hearing.