ANCHORAGE (AP) — Six Alaska Native corporations have pledged at least $500,000 to fight efforts to repeal the state’s new oil tax structure.

The coalition, “No One on One,” is joining other business-supported organizations in opposing the referendum, scheduled for the August primary ballot. Another group, the oil-industry backed “Vote No on One,” has reported raising at least $9.5 million.

The coalition includes Arctic Slope Regional Corp., Cook Inlet Region Inc., Doyon Ltd., NANA Regional Corp., Bristol Bay Native Corp. and Bering Straits Native Corp. Some of the corporations have substantial oil-field business, the Anchorage Daily News reported (http://bit.ly/RGfjNR ). Wednesday’s announcement was held at a fabrication shop owned by a subsidiary of Arctic Slope Regional Corp.

Representatives of all six corporations say the tax cut is promoting more jobs and oil industry investment. They say their shareholders are benefiting. Tara Sweeney, senior vice president of Barrow-based Arctic Slope Regional Corp., said the group is an outgrowth of the 2010 effort to re-elect U.S. Sen. Lisa Murkowski as a write-in candidate. That effort involved regional and village corporations and the Alaska Federation of Natives. Sweeney said she hoped the other Native organizations would join the “vote no” effort.

The president of the Alaska Federation of Natives says that group doesn’t plan to take sides in the oil tax debate. A spokesman for Juneau-based Sealaska Corp. said it won’t join the coalition.

Byron Mallott, a former Sealaska CEO who is currently a Democratic candidate for governor, plans to support the repeal effort. But he said he understands why the corporations are opposing the referendum.

“Those corporations that are supporting the ‘Vote No’ effort have strong ties to the oil industry in terms of work that they do in that industry,” Mallott told the newspaper in an interview. “It’s surely in their corporate interests to have the best relationships with the industry, and with the business community that supports, and is sustained by, the industry.”

He said the regional corporations not joining the coalition don’t have those ties.

Supporters of the referendum expect to be hugely outspent but think voters will support repealing a tax structure they see as a giveaway to industry with no guarantee for what Alaska will get in return.