With a slap at Republican Gov. Bill Clements, a three-judge federal panel has handed down a new congressional redistricting plan for Texas that sharply alters parts of the plan approved last summer by the Texas legislature.

The judicial plan overturned an attempt by Republicans and some minorities in the Dallas area to create a new minority district, in the process eliminating a safe Democratic seat. The judges also redrew the boundaries between two south Texas districts that had been criticized by the U.S. Justice Department as violating the Voting Rights Act. The effect of the changes is an apparent boost for the Democrats, who now hold 19 of the 24 congressional seats in Texas.

Spokesmen for the party said today the new plan, which adds three seats because of population gains, could end up with a 21-to-6 Democratic advantage.

The proposal approved by the Texas legislature last summer was initially seen as a strongly Republican plan. Republicans still hope to capture more than six seats under the new map.

The three-judge panel, in a ruling issued Saturday, accepted most elements of the plan approved by the legislature, changing six of the 27 districts. But in sometimes harsh language, it criticized the efforts of Clements and the Democratic-dominated legislature to draw a minority seat in Dallas.

Under the legislature's plan, Rep. Martin Frost's 24th District became the new minority district, with Hispanics and blacks constituting about 64 percent of the population.

Those changes turned Rep. Jim Mattox's marginally Democratic 5th District into a potential Republican stronghold.

But the panel, in a split decision, decided the effect was "severe retrogression" for Dallas County minorities.

The lines for the Dallas-area districts approved by the judicial panel would make Frost's district about 45 percent minority, Mattox's about 32 percent.

Mattox has filed for state attorney general, and two attractive young Republicans were waging a spirited contest for the 5th District. But under the judicial plan, they do not even reside in the new 5th District.

The changes in the two south Texas districts should have little impact on party strength in Congress. Both are considered Democratic seats. The Justice Department objected to the unequal balance of Hispanics in the two districts and the three-judge panel remedied that.