A federal appeals court on Tuesday blocked elections in Boston this fall for 17 state House seats, saying a redistricting map approved by lawmakers in 2001 deprived black voters of their constitutional rights.

The three-judge panel ordered lawmakers to submit a new plan for the districts within six weeks.

The judges determined the redistricting plan deprives black voters of equal opportunity "to participate in the political process and to elect representatives of their choice."

Secretary of State William Galvin warned candidates to stop collecting signatures, due April 27, until a new map is in place.

"I don't think it's too much of an exaggeration to say that it throws the electoral process into chaos," Galvin said. "For those legislators who are in these districts, it creates a great deal of uncertainty about their political futures."

Plaintiffs who challenged the map last year claimed it violated the Voting Rights Act (search) and the U.S. Constitution. They did not have to show blatant discrimination, only that the final plan had a discriminatory effect, according to the ruling issued by the U.S. 1st Circuit Court of Appeals (search).

While the map provides white voters with a number of majority white districts, it "fails to provide African-American voters with a proportional number of majority black districts," the judges wrote.

Activists who brought the suit said they were encouraged by the decision.

"This is a textbook case of packing people of color into as few districts as possible, minimizing their opportunity to elect a representative of their choice," said Atiya Dangleman, program director of Boston VOTE.

Some of the districts affected by the ruling are held by top House leaders, including House Speaker Thomas Finneran, House Majority Leader Salvatore DiMasi and Judiciary Committee Chairman Eugene O'Flaherty, all Democrats.

A spokesman for Finneran offered reporters a statement from Democratic state Rep. Thomas M. Petrolati, chairman of the House Redistricting Committee.

Petrolati defended the map-making process, noting the committee held five public hearings before drafting the final version.

"Committee members designed a redistricting map that met the three court requirements of keeping together communities of interest, not deviating population by more than 5 percent and making districts contiguous," he said, promising to draft a new map by the court's deadline.

The judges also criticized the House for drawing the map to protect veteran House members "without pausing to investigate the consequences of its actions for minority voting opportunities."

Boston's minority population exceeded 50 percent for the first time in the 2000 Census.