Charging that the Democrats are "stonewalling," House Republicans will introduce a motion today asking that a select committee be appointed to investigate alterations in transcripts of published House committee hearings.

Rep. Judd Gregg (R-N.H.) aired the issue on the floor of the House yesterday afternoon, revealing that his office had come upon two more instances, in separate subcommittee hearings, of apparent tampering, in addition to an initial set of alterations already referred to the House Standards of Official Conduct Committee for investigation.

"Now, this is not an isolated case," Gregg said, suggesting that the problem may be far more widespread than first suspected. "The severity of this threatens the ability of this Congress to function effectively."

Almost two weeks ago, seven Republican members of Congress charged that statements they and witnesses had made during joint hearings of five subcommittees on the Environmental Protection Agency had been altered between transcription and official publication.

The Republicans contend that the alterations in most cases make them look foolish. They have singled out the majority staff of the panels involved as the probable source of the tampering, and demanded an open probe. The matter was referred to the ethics committee for investigation, but Republicans have objected. On the floor yesterday, Gregg said that panel was inappropriate not only because its probes were done in secret, but because it was charged only to look into the initial tampering instance, not any other episodes.

The resolution requesting a select committee to investigate will be broad enough to permit a probe of all potential alterations. It must be approved by a vote of the full House.

According to a Justice Department spokesman, falsifying official government documents is punishable by a fine of up to $10,000 and imprisonment of up to five years.