PORTLAND —  A panel of federal judges ruled this afternoon that Maine will have to redraw its congressional districts to reflect population shifts in time for the 2012 elections rather than the following year.

Two Cape Elizabeth residents filed a lawsuit against state officials that argued that district boundaries need to reflect the most current census data in time for the congressional elections. The plaintiffs, William Desena and Sandra Dunham, argued that their votes would be diluted if the boundaries remained unchanged. The census indicated that the 1st District, in the south, has a population of 668,515 residents while the 2nd District had 659,848 – a difference representing about 0.65 percent of the total state population.

Judge Bruce Selya, the chair of the three-member panel, said the judges were unanimous in their decision that redistricting must take place before the election. Selya said the judges wrestled with how the redistricting should take place. He said the court must balance its responsibility to see that its decision is carried out with the state’s sovereign interest in having a say in the procedure.

Selya instructed the three parties – the Maine Democratic Party is an intervenor – to submit proposals by next Friday. Each will have until the end of the following Monday to comment on one another’s plans.

The panel announced its decision after a short recess following oral arguments at U.S. District Court this morning. The plaintiff’s lawyer, Timothy Woodcock, and Deputy Attorney General Paul Stern agreed that it would be unconstitutional to hold the elections using outdated census data. Janet Mills, arguing on behalf of the Democratic Party, disagreed and stressed the need for a methodical, bipartisan process.

The panel took the unusual step of telling the parties their decision before issuing a written order because of the tight time constraints, according to Selya, a member of the 1st Circuit Court of Appeals in Boston. Judges George Singal and D. Brock Hornby were the other panel members.

The petitions for congressional candidates are available starting Jan. 1, 2012, the submission deadline is March 15 and the primary is on June 12.

Since 1993, congressional redistricting in Maine has been tied to state legislative redistricting. A change in state statute required congressional redistricting to take place that year and every 10 years after, using a bipartisan member commission. The plan would need to be approved by a supermajority of both chambers of the Legislature. The Maine Supreme Judicial Court makes the apportionment if the Legislature fails to do so within the specified time frame.