A key House Republican said yesterday GOP legislators will be using "extremely unpleasant and disruptive" tactics at the opening of Congress next week to protest the refusal of House Democrats to change the ratio of party strength on the vital Ways and Means Committee.

"We have no choice but to raise hell," said Rep. Barber B. Conable Jr. (R-N.Y.), the ranking minority member of Ways and Means, which handles tax, trade and Social Security bills. Conable said the tactics were forced by the insistence of Speaker Thomas P. O'Neill Jr. (D-Mass.) and the House Democratic Caucus on maintaining virtually a 2-to-1 majority on Ways and Means, even though the November elections reduced the Democratic majority in a whole House 5 to 4.

The Democratic Caucus last month ordered that the Ways and Means ratio be 23 to 12, one that Conable said virtually guarantees defeat for any Republican initiative in the committee.

Conable said he had told the new committee chairman, Rep. Dan Rostenkowski (D-Ill.), that either 20 to 12 or 23 to 14 would be agreeable. "I don't want to start out harassing my new chairman," he said, "but this is not acceptable."

Conable said there will be "delaying tactics" and other "disruptive" actions -- what he called "floor rumbles" -- to dramatize for the public what he called "the unfairness" of the Democrats' position.

Rostenkowski, in a telephone interview from Chicago, said he personally would accept a 22-to-12 Democratic margin but was bound by the caucus decision. "I know Barber is concerned that there won't be a conservative attitude in committee, reflecting the election results, but I disagree. . . . I'm not going to obstruct this president. I'll be with him on everything that is reasonable."

Ari Weiss, an aide to O'Neill, said it was traditional for the majority party in the House to take a larger share of seats on the key committees than it held in the House as a whole. "We're doing the same thing the Republicans did the last time they were in control," he said. Weiss pointed out that in 1953, when Republicans had only a 10-seat majority in the House, they had a 15-to-10 ratio on Ways and Means.