AUGUSTA, Maine — Calling it a top priority of his administration, Gov. Paul LePage on Tuesday signed into law a bill designed to lower health insurance costs and cover more Mainers through a series of market changes including a new high risk pool and allowing smaller companies to band together to get better rates.

Backed by dozens of Republican lawmakers who supported the bill, LePage thanked party leaders who shepherded the bill through grueling House and Senate debates, making it the biggest political trophy for the GOP so far this session.

“This legislation has been a top priority,” the governor said during the State House bill-signing.

“Most importantly, this will create choice for Mainers,” LePage said. “This will lower health care costs for Mainers. This will help Maine small businesses. This will create more jobs for Maine people. This is a step in the right direction. This legislation is going to drive health care costs down so we can be competitive with our neighbors.”

But even before LePage had signed his name on the bill, Democrats branded it “reckless” and said it would hurt Mainers over age 48 and those living in rural areas, who stand to see higher rates. They also took aim at a provision to add a $4 charge to the monthly premium of every Mainer with private coverage. The fees will pay for a high risk pool that will cover Mainers with high health care expenses.

Maine Democratic Party Chairman Ben Grant labeled the charge a tax, and said its enactment by a party that abhors tax increases “is hypocrisy of the highest order.”

Meanwhile, the health care activist group Maine People’s Alliance said it’s considering launching a people’s veto referendum campaign to stop the law from taking effect. Calling the bill a “handout to the insurance companies,” the alliance also expressed worries about the impact on older and rural Mainers.

“There’s only one way to stop it now, and that’s at the ballot box,” read a blast email from MPA executive director Jesse Graham. The organization is seeking volunteers willing to gather the approximately 60,000 signatures needed to put the issue before Maine voters. By state law, the gathered signatures would have to be submitted to the Secretary of State’s office within 90 days of the adjournment of the current Legislative session scheduled for June 15.

“We’re just testing the waters … it would be a significant undertaking,” Graham said in a phone conversation. Among other supporters of the new law, the insurance industry likely would fund a major campaign to defeat the referendum, he predicted.

Nearly 6,000 people, including about 1,500 members of the Maine Small Business Coalition, signed a petition last week in protest of LD 1333 prior to its approval by the Legislature. The coalition represents about 2,500 sole proprietors and small businesses with an average of four employees.

“A huge number of our membership is deeply concerned” about the provisions of LD 1333, which would disproportionately affect older Mainers in rural areas, said coalition director Nathan Libby.

Republicans dismissed opponents’ claims.

Rep. Andre Cushing of Hampden, the assistant House GOP leader, said the $4 “assessment” will replace a charge on health insurance claims Mainers have been paying to keep the Dirigo Health program — the previous administration’s attempt at health insurance reform — in operation. The LePage administration wants to phase out Dirigo.

“So this $4 assessment could be more than an offset for what people are paying now,” said Cushing. “It could be considerably less than what they are now paying.”

In addition to the risk pool, the new law will allow companies with fewer than 50 employees to band together to create larger insurance pools to obtain better rates.

Mainers buying individual insurance, not through employers, could buy policies from companies based in New Hampshire, Massachusetts, Rhode Island and Connecticut starting in 2014, the same year a similar provision kicks in under the national Affordable Care Act.

The law will also change Maine’s community rating policy so the differential in rates gradually increases. While the expanded “rating bands” will allow insurers to charge significantly less to younger, healthier Mainers and spread the risk over a larger pool, they could also mean higher rates for those who are older, sicker and live in rural areas.

House Speaker Robert Nutting, R-Oakland, said the bill is based on proven systems in dozens of other states where rates are lower.

But Senate Democratic Leader Barry Hobbins of Saco said the bill was rushed through without a comprehensive actuarial analysis by the state Bureau of Insurance.

BDN reporter Meg Haskell contributed to this report.