OLYMPIA — Responding to criticism leveled at him last week, Gov. Jay Inslee on Thursday challenged two Republican senators to “do more than just criticize and mischaracterize” actions being considered to reduce carbon pollution.

The governor sent a letter to Sens. Doug Ericksen, R-Ferndale, and Curtis King, R-Yakima, disputing their assertions that the Legislature has been cut out of the process of evaluating potential requirements for cleaner transportation fuels.

The legislators wrote to Inslee last week, saying it was “extremely troubling” that he seems to have skipped lawmakers on such a major policy decision. They said a low-carbon fuel standard would hurt consumers and warned that Inslee’s climate proposals could devastate the state’s economy.

Inslee responded Thursday that the process has been open and transparent, lawmakers and legislative staff have been included, and the senators’ assertion that costs could exceed $1 a gallon was incorrect.

“I can assure you that no proposal from me that adds costs at the pump even near your asserted costs, will ever materialize,” Inslee wrote.

He added that no decision has been made on a specific proposal, and that any decision would trigger an extensive public review process.

The governor has said he could take executive action on a policy to require cleaner fuels, but he reiterated in his letter that he has made no decision, which Ericksen said is part of the problem.

“They don’t have a plan ready to go,” he said. “There is no legislation for me to be for or against.”

A low-carbon fuel standard would require fuel producers over time to gradually offer a mix of cleaner alternative fuels such as biofuels, biodiesel or natural gas. The idea is to reduce greenhouse gas emissions from driving, since transportation accounts for nearly half of Washington’s carbon emissions.

Republican leaders and other critics have seized on a figure of a $1-a-gallon increase for gasoline, based on a 2012 Boston Consulting report commissioned by the Western States Petroleum Association.

Inslee pointed to an analysis released last month by the state Office of Financial Management that found gas prices would increase by 2 cents in 2020 to 10 cents by 2026, under certain assumptions. But the senators noted that under another scenario, gas prices could increase more than 20 cents a gallon.

King, who co-chairs the Senate Transportation Committee, said he’s willing to continue working with the governor on the issue, “but we have to get real about the impact on the citizens of the state of Washington, and I don’t think we’re there yet.”

Ericksen, who is a member of the transportation committee and heads another committee dealing with energy and environment issues, said he disagreed with the governor’s assertion that they haven’t offered real solutions.

“We’ve been very proactive on ideas that are going to be clean energy,” he said, adding, “What I’m going to pursue is an energy future for Washington state that’s based in the realities of today, where I can keep energy costs low while we’re making it cleaner over time.”