AUGUSTA — A top Maine business group said Wednesday that it opposes Question 1 on the November ballot, saying the election reform effort’s funding mechanism — rolling back corporate tax breaks — would harm the state’s business climate.

The Maine State Chamber of Commerce is the most prominent group to oppose the question since supporters of the effort started campaigning in July. Proponents have raised more than $1.3 million and their effort has gone relatively unanswered until recently.

Question 1 would expand Maine’s taxpayer-funded campaign system, the Maine Clean Election Act, increasing its allocation from $4 million to $6 million in each two-year budget and making more money available to publically funded legislative and gubernatorial candidates.

The chamber’s only sticking point is the funding mechanism over that two-year period: The proposal asks legislators to eliminate $6 million in “low-performing, unaccountable” corporate tax breaks “with little or no demonstrated economic development benefit.”

The Maine State Chamber of Commerce announced a Thursday news conference in Portland on Question 1. Dana Connors, the chamber’s president, said Wednesday he didn’t want to discuss their argument in full ahead of the event, but he spoke generally about it.

“The fact that we’re taking $6 million out of business incentive programs that are intended to grow the economy and create jobs but instead using it to elect candidates,” he said, “our economy simply cannot afford that.”

Mainers for Accountable Elections, the coalition running the pro-Question 1 campaign, fired back in a statement, saying eliminating low-performing tax breaks won’t hurt the economy.

“It’s unfortunate to see the Maine State Chamber of Commerce making a decision based on false information when, in fact, Question 1 will strengthen our democracy, increase transparency and elevate the voice of everyday Mainers in our elections,” said Andrew Bossie, the coalition’s president.

Business tax breaks have been a bone of contention in Maine: The state spends more than $100 million on incentives defined as risky by a state audit, the Maine Center for Public Interest Reporting said in 2013, and legislators have struggled to quantify them over the years.

Connors for years has defended Maine’s overall business incentive program, saying it’s modest compared to other states’ packages and that for legislators, identifying low-performing breaks will be difficult.

“While those words may suggest one thing, I think you’ll find, as the Legislature has found in the past, that we do not have a robust economic development program,” he said.

So far, opposition to the referendum has mostly come from Maine conservatives ideologically opposed to expanding publicly funded elections: Gov. Paul LePage, a Republican, called the referendum a “scam” last week at a news conference with members of Mainers Against Welfare for Politicians, a group formed to oppose the question.