Congressional Republicans learned yesterday that they have no legal remedy to their complaints that the Democratic majority in the House has refused to give them a fair share of committee seats in recent years.

A panel of U.S. Court of Appeals judges, ruling on a lawsuit brought by 14 House Republicans last session, decided that the Constitution's separation-of-powers clause compelled the court to stay out of such internecine congressional disputes.

"Separation-of-powers concerns counsel us not to exercise our judicial power," wrote Judges Roger Robb and James F. Gordon . . . . "One can readily see the wisdom of not interfering with the House's method of allocating committee seats."

The Republicans charged that although they comprised more than 44 percent of the membership in the 97th Congress the Democrats had given them only 40 percent of the seats on the Budget and Appropriations panels and only 31 percent on Rules, three of the most powerful committees in the House.

These allocations, the Republicans said, unfairly diluted their party's legislative influence and, in effect, disenfranchised the voters who had elected them.

A House Republican spokesman said that he was aware of no further plans to seek legal action against the Democratic leadership, even though Democrats again took a disproportionate share of seats in the reorganization of committees for the 98th Congress this month.

In most House committees, Democrats, who now comprise 61 percent of the House, took between 64 and 69 percent of the subcommittee assignments.

"There's nothing much we can do about it," said Rep. James T. Broyhill (R-N.C.), ranking minority member of the House Energy and Commerce Committee, which this week assigned Republicans only 31.1 percent of its subcommittee seats. "It's power politics, and it flies in the face of President Reagan's plea for bipartisanship. I'm afraid our only response might be equal partisanship."

Broyhill said that in the case of his committee it might mean that Chairman John D. Dingell (D-Mich.) will find less Republican support for his attempts to amend the Clean Air Act to the liking of auto makers in Dingell's suburban Detroit district.

"The chairman is going to find that for a lot of things he wants our support might not be there," Broyhill said.