BOSTON – Lawmakers overwhelmingly approved a bill Tuesday that would make Massachusetts the first state to require that all of its residents have some form of health insurance.

The plan – hailed as a national model and approved just 24 hours after the final details were released – would dramatically expand access to health care over the next three years.

If all goes as the supporters hope, those already insured will see a modest drop in their premiums, lower-income residents will be offered new, more affordable plans and subsidies to help them pay for coverage, and those who can afford insurance but refuse will face increasing tax penalties until they obtain coverage.

The House approved the bill on a 154-2 vote. The Senate endorsed it 37-0.

The bill now heads to the desk of Gov. Mitt Romney, a potential Republican candidate for president in 2008. Romney spokesman Eric Fehrnstrom said late Tuesday the governor will sign the bill.

Lawmakers hailed the legislation.

“It’s only fitting that Massachusetts would set forward and produce the most comprehensive, all-encompassing health care reform bill in the country,” said House Speaker Salvatore DiMasi, D-Boston. “Do we know whether this is perfect or not? No, because it’s never been done before.”

The cost of the bill will rise from an estimated $316 million in the first year to more than a $1 billion in the third year, with much of that money coming from federal reimbursements and existing state spending. About $125 million in new money will come from the state’s general fund during each of the three years.

The measure does not call for new taxes, but would require businesses that do not offer insurance to pay an $295 annual fee per employee.

The only other state to come close to the Massachusetts plan is Maine, which passed a law in 2003 also designed to dramatically expand health care. That plan relies largely on voluntary compliance.

The Massachusetts plan is unique in requiring both employers and residents to contribute to a system to cover nearly all of the state’s 500,000 uninsured.

“What Massachusetts is doing, who they are covering, how they’re crafting it, especially the individual requirement, that’s all unique,” said Laura Tobler, a health policy analyst for the National Conference of State Legislatures.

The plan hinges in part on two key sections: the $295-per-employee business assessment and a so-called “individual mandate,” requiring every citizen who can afford it to obtain health insurance or face increasing tax penalties.

Liberals typically support employer mandates, while conservatives generally back individual responsibility.

“The novelty of what’s happened in this building is that instead of saying ‘let’s do neither,’ leaders are saying ‘let’s do both,”‘ said John McDonough of Health Care for All. “This will have a ripple effect across the country.”

The bill is intended to alter the state’s health care landscape in large and small ways.

The state’s poorest are the biggest winners. Single adults making $9,500 or less a year will have access to health coverage with no premiums or deductibles.

Those living at up to 300 percent of the federal poverty level, about $48,000 for a family of three, are also big winners. Under the bill, they will be able to get health coverage on a sliding scale also with no deductibles.

The vast majority of Massachusetts residents who are already insured could see a modest easing of their premiums.

Not everyone may be thrilled with the changes. Individuals deemed able but unwilling to purchase health care could face fines of more than $1,000 a year by the state if they don’t get insurance.

To help people find insurance, the bill creates something called a health care “connector” which encourages private health insurers to provide affordable policies to small businesses and individuals.

Romney, who pushed vigorously for the individual mandate, called the legislation “something historic, truly landmark, a once in a generation opportunity.”

The $295-per-employee assessment is expected to get extra scrutiny from Romney who is opposed to new taxes and has the ability to veto individual portions of the bill. Romney said the assessment wasn’t a “broad-based tax.”

Fehrnstrom said Romney will sign the bill, but will recommend changes.

“We look forward to signing it sometime next week. As with any appropriations bill, the governor will use his powers to make some modifications and adjustments, but they won’t affect the main purpose of the bill,” he said.

The Democrat-controlled Legislature could easily override a veto.

Another goal of the bill is to protect $385 million pledged by the federal government over each of the next two years if the state can show it is on a path to reducing its number of uninsured. The U.S. Department of Health and Human Services has threatened to withhold the money if the state does not have a plan up and running by July 1.