BANGOR, Maine — Two small business owners who already pay their employees more than the minimum wage spoke at a press conference on Wednesday about a citizen-initiated referendum effort to raise the state’s base pay from $7.50 per hour to $12 by 2020.

“For me, this is really a fairness issue,” Jonathan Fulford, owner of Artisan Builders of Monroe, said about why he pays his 10 employees at least $15 an hour.

Elena Metzger, owner of Northeast Reprographics in Bangor, said her six employees make at least $13 an hour.

“To keep my experienced staff, I pay a fairness wage,” Metzger said at the press event organized by the Maine Small Business Coalition.

Bangor City Councilor Gibran Graham, who is the marketing manager for The Briar Patch bookstore where the gathering was held, said anyone who works full-time, be it at one job or three, deserves to earn a living wage. He added that increasing employee wages is also good for the local economy because employees purchase more.

The referendum campaign is spearheaded by the Maine AFL-CIO and the Maine People’s Alliance, a liberal-leaning advocacy group, and kicked off in April. The Maine Small Business Coalition is a partner of the MPA. The groups need to gather more than 60,000 signatures to get the minimum wage referendum on the ballot in 2016.

“We are already one quarter of the way to meeting our goal,” Kate Hall, Bangor field manager for the Maine People’s Alliance, informed the gathering, which included local media, presenters and a few others.

The plan would increase Maine’s minimum wage to $9 per hour in 2017 and by an additional dollar per hour each year until 2020 to reach $12 an hour. After that, the state’s minimum wage would rise or fall based on the cost of living, using the consumer price index, Hall said.

The Maine chapter of the National Federation of Independent Business, a conservative advocacy group, called the press gathering all “smoke and mirrors,” saying it ignores the “burdensome economic impact” that raising Maine’s minimum wage will have on small business owners and the people that they employ.

“We agree with the desire to increase people’s earnings but disagree strongly with the method being proposed,” David Clough, the federation’s Maine state director, said Wednesday. “We feel that building a strong economy, by helping businesses get started and create jobs, is a better approach.”

The move would be expensive for employers, and would be especially hard on small businesses, Clough said.

“A $12 minimum wage would add almost $10,000 a year to the cost of hiring someone at minimum wage,” he said. “These costs have to be paid for. Research shows us that they will be paid for in higher prices and other adjustments. It’s not a free lunch.”

Bangor and Portland have recently discussed raising the minimum wage within city limits, with Portland city leaders voting in July to increase the minimum wage to $10.10 effective in January, and Bangor city leaders deciding this week to delay consideration of City Councilor Joe Baldacci’s local minimum-wage increase proposal until after the November election.

MPA has said a living wage for a single adult in Maine is about $15.82 per hour and that more than half the job openings in Maine pay less than that. The Maine AFL-CIO has named raising the minimum wage as one of its top priorities this year.

The names of more than 150 small businesses from across the state that support the plan were released at the gathering and Will Ikard, director of the Maine Small Business Coalition, said in a press release that these business owners “know that raising the minimum wage will be a boon for businesses and employees alike.”

“It’s good for our people,” he said at the gathering.