Opponents of a controversial carbon tax that will push up the price of gas are lobbying a consortium of mid-Atlantic states to reject an agreement Massachusetts struck last month with several other states in an effort to doom the deal.

“TCI is a poor concept that is fundamentally regressive, economically damaging and places an unnecessary financial burden on people who can least afford it. Please reject it,” Massachusetts-based Citizens for Limited Taxation wrote in an open letter signed by 20 other groups.

The Transportation Climate Initiative championed by Gov. Charlie Baker aims to reduce motor vehicle pollution by at least 26% and generate over $1.8 billion in Massachusetts by 2032, according to a deal Massachusetts signed with Rhode Island, Connecticut and Washington, D.C. It will up the price of gas by 5 to 7 cents per gallon, according to state estimates. Eight other states are still considering the deal.

Chip Ford of CLT told the Herald he’s concerned over the “lack of accountability” the program creates and said tax increases should be a function of the Legislature, not the governor alone. He hopes that if other states fail to sign on, the program will run out of gas.

He also argued the cap-and-invest program would cost low-income residents the most, as companies will pass costs along to the consumer.

The state has yet to lay out its plans for spending the roughly $160 million that will be raised annually through the program. A minimum of 35% of the proceeds will be reinvested in communities most affected by air pollution, but Stacy Thompson of the Liveable Streets Alliance said it isn’t enough.

“Even the best case scenario for TCI is just not enough to meet the full scope of the transportation challenges we’re facing,” Thompson said.

Baker spearheaded the TCI agreement and touted the December agreement as a major victory for his administration. But the Republican governor has since issued a series of vetoes that Thompson called “an economic slap in the face.” Baker struck down the Legislature’s attempts to impose a series of benchmarks that would have set the state on a course to achieve is “net-zero” carbon goals for 2050 and gutted its efforts to cut costs for low-income MBTA riders by levying higher fees on ride-hailing apps like Uber and Lyft.

“There’s a disconnect,” Thompson said. “We’re not matching resources to the needs of the state and that should worry people.”

The state has committed to a public process to determine how reinvestment funds are spent but has yet to lay out those plans.