PORTLAND – Credit card giant MBNA has joined several of the state’s other large employers in a campaign against a Maine casino.

The Delaware-based company announced Friday it is joining the effort by Casinos No to defeat a November referendum question that could allow the Penobscot and Passamaquoddy tribes to build the state’s first casino resort in Sanford.

“We don’t feel a casino is appropriate for Maine,” Carolyn Marsh, a Maine spokeswoman for the corporation, said.

MBNA, which came to Maine in 1993 and now has offices throughout the state, found success by creating credit cards for organizations that encourage employees, alumni and other customers to make purchases with them. The firm issues branded cards for six casino companies. Casino proponents said MBNA opposes the project because it does not want to compete with a casino that would offer higher wages and better benefits to service employees.

“MBNA should be using its resources, some of which have been made off the casino industry, to provide its own workers with living wages,” Erin Lehane, spokeswoman for the pro-casino group Think About It, said.

Marsh would not say whether the prospect of competition for labor played a factor in MBNA’s decision.

Ed Gorham, executive director of the Maine AFL-CIO, said he thinks large companies like MBNA and L.L. Bean are opposing the casino out of self-interest.

“They don’t want to see anything where workers are going to make a decent wage as a result of a collective bargaining agreement,” he said.

Tribal officials have not committed to using union labor in the casino or resort.

But under an agreement reached with unions last month, contractors who build the casino would receive wages determined by both the developer and a council of labor unions.