A new super PAC partnership between billionaire environmentalist Tom Steyer, the AFL-CIO and major public sector employee unions has triggered an angry backlash among the building trade unions — dividing organized labor just as it ramps up its 2016 political programs.

In letters delivered Monday to AFL-CIO President Richard Trumka, the presidents of eight building trade organizations called on the AFL-CIO to cut ties with Steyer, whose opposition to an extension of the Keystone XL Pipeline infuriated unions that had championed the jobs that the oil pipeline would have created.

“A growing trend within the federation seems to consistently minimize the importance of building trades jobs and our members’ livelihoods in the pursuit of a coalition strategy with outside organizations that has produced mixed results at best and disastrous results at worst for our members and their employment prospects in many instances throughout the country,” the building trade presidents wrote in a letter obtained by The Washington Post.