Continuing a decades-old dispute, General Electric Co. is sharply objecting to a new federal plan that would force it to spend hundreds of millions of dollars to remove massive amounts of toxic chemicals from the Housatonic River, which the company polluted for nearly 50 years.

The industrial giant, which last month said it will move its headquarters from Fairfield, Conn., to Boston, contends it should be allowed to dispose of dredged pollutants in landfills near the river in the Berkshires, despite state regulations that require the toxic sludge to be taken out of Massachusetts.

In a letter to the US Environmental Protection Agencylast month, company officials argued it should be exempt from state hazardous waste regulations and other environmental rules.

In October, the agency released a plan that would require GE to spend an estimated $613 million to remove large amounts of polychlorinated biphenyls, toxic chemicals known as PCBs, that a company plant in Pittsfield dumped into the river from the 1930s to the 1970s. PCBs, banned by the federal government in 1979, were once ubiquitous as coolants and insulating fluids.

But GE officials label the government’s “rest of the river’’ cleanup plan “arbitrary and capricious’’ and say it violates the terms of a 2000 settlement among the EPA, the company, and state and local officials.

“The inevitable negative impacts … are dismissed and cost considerations are ignored,’’ wrote Ann Klee, GE’s vice president of global operations, in the letter.

Company officials say they have already spent more than $500 million since the 1990s to clean two miles of the river closest to the plant and on related environmental projects in the area. But the company acknowledges that contaminated soil still stretches along more than 10 miles of the river, its banks, and its floodplains between Pittsfield and Lenox. The Housatonic runs nearly 150 miles from Western Massachusetts through Connecticut to the Long Island Sound.

Environmental advocates argue that the agency’s plan does not go far enough to reduce the pollution, noting that a significant amount of PCBs would remain in the river.

“We think this is one of the EPA’s weakest cleanups that has ever been put out,’’ said Tim Gray, executive director of the Housatonic River Initiative, an advocacy group in the Berkshires. “It’s very frustrating.’’

He denounced GE’s opposition to the plan as “an outrage’’ and said he was worried that the company’s move to Boston would increase its political power on Beacon Hill.

“Their influence all along has been to weaken the cleanup – every step along the way,’’ Gray said. “Their press releases say that they want to do what’s best for the river, but then they put out videos saying that cleaning the river will destroy it.’’

Klee said the company opposes the agency’s insistence that it move more than 1 million cubic yards of polluted sediment,through thousands of truck or rail trips, to a federally licensed disposal site outside Massachusetts. GE estimates shipping the sediment out of state could cost the company more than $250 million.

The company argues it shouldn’t have to remove the dredged soil from the state, because it wasn’t required to do that in the first phase of the cleanup, which was completed in 2006. The proposed out-of-state location hasn’t been designated yet.

“Out-of-state disposal will be no more protective of human health or the environment than on-site disposal in a secure, state-of-the-art facility, but it will cost about a quarter of a billion dollars more,’’ Klee wrote.

The company also dismissed the need to comply with state regulations that limit where solid waste facilities can be built, such as those that would store the dredged sediment from the river.

“These regulations should be waived in their entirety,’’ company officials wrote in a formal objection to the plan.

GE also opposes the agency’s plan for it to dredge some 340,000 cubic yards of sediment from a portion of the river known as Woods Pond, where the highest concentrations of carcinogenic chemicals remain. The company says it should have to remove only about 13 percent of the sludge.

“EPA’s Woods Pond requirement alone will add an estimated $130 million to the cost of the remedy, for no environmental benefit,’’ Klee wrote.

EPA officials defended their plan, which they say would reduce PCB levels in the river’s fish by 95 percent over the next 13 years.

“We find those to be acceptable levels,’’ said Jim Murphy, an EPA spokesman based in Massachusetts. “We’re getting out of the river what we need to get out to protect human health and the ecosystem.’’

Murphy acknowledged the criticism from both sides and said the agency was mindful of costs in designing its plan. Environmental advocates lobbied for a cleanup that would have cost more than $1 billion, he said, while reducing the toxic chemicals in the river’s fish by only slightly more.

The agency considers the dredging of Woods Pond and removing the toxic chemicals from the state to be necessary expenses,Murphy said. He noted that some of the state regulations requiring the removal of the dredged sediment from Massachusetts were passed after the completion of the first phase of the cleanup.

But GE called the agency’s plan “unlawful’’ and said it was starting an appeals process with the agency.

If the EPA and the company fail to find common ground, GE could contest the plan in federal court, further delaying the cleanup

David Abel can be reached at dabel@globe.com. Follow him on Twitter @davabel.