The union trying for years to organize Walmart workers employs non-union staffers — and fired several of them 15 months ago when they attempted to organize, one former insider claims.

The United Food & Commercial Workers International employed the non-union workers as part of its national OUR Walmart campaign.

Those fired were Seattle-based organizers who said the dismissals came several months after they reached out to the union that represents UFCW employees, the insider told The Post.

They wanted to know why they were not covered by the same contract as their colleagues.

“As union organizers, it’s our job to teach people about their labor rights and how to be more effective at Walmart,” said one of the fired UFCW employees, who did not want to be identified.

The UFCW “is all for workers’ rights yet it denied its own staff union contracts and didn’t pay us overtime and eventually fired us for reaching out to a union,” the ousted worker said.

A senior UFCW official on Wednesday referred questions about the firings to its OUR Walmart campaign directors at the time.

Two campaign directors who oversaw the allegedly ousted workers were themselves fired in June 2015. That pair would have been responsible for any actions against their staff organizers, the UFCW official said.

“We do not fire people for union activity,” the official said.

One of the fired OUR Walmart directors about whom the UFCW official was referring, Daniel Schlademan, disagreed with the UFCW’s version of how the organization made personnel decisions.

“Any staffing decisions on the Making Change at Walmart campaign were made solely by UFCW’s human resources department,” said Schlademan, who is now spearheading another OUR Walmart campaign, with 20 social justice and labor groups.

FAIR, the Federation of Agents & International Representatives, which represents UFCW workers, including organizers and office workers, would be responsible for investigating why five of the 10 OUR Walmart workers in the Seattle office were not union members, one ousted worker said.

FAIR President Steven Marrs declined to comment beyond saying the workers were not members of FAIR.

According to the fired worker, however, Marrs did reach out to OUR Walmart honchos Schlademan and Andrea Dehlendorf, requesting meetings and employment documents.

It’s been 18 months since the Seattle workers were fired and about nine months since they’ve heard from Marrs.

There has been no settlement payment. A senior UFCW official said arbitration proceedings were never initiated, but that FAIR did file a grievance over temporary workers that has since been settled, the official said.

The fired employees weren’t temps, rather they had worked full-time for three years.

The fired workers earned about $10,000 a year less than their unionized peers in the same office, the ousted worker said. They also were denied overtime pay and regularly worked 50-hour weeks.

Before they were fired, they organized a big push at Walmart in preparation for a rolling strike across the country in June 2014.

“The three of us got the turnout of Walmart workers in Seattle who were part of the strike,” said one of the Seattle employees. “The next week they fired us.”