Billionaire environmental activist Tom Steyer addresses the March to Break Free From Fossil Fuels on May 14 in Los Angeles. (David McNew/AFP/Getty Images)

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.

"The AFL-CIO has now officially become infiltrated by financial and political interests that work in direct conflict to many of our members’— and yes, AFL-CIO dues-paying members’ lives," the letter continued. "This is a disturbing development and one that requires a further explanation."

The missive was signed by the heads of the North America’s Building Trades Unions; the Laborers’ International Union of North America; the International Union of Operating Engineers; the International Association of Heat and Frost Insulators and Allied Workers; the United Association Union of Plumbers, Fitters, Welders, and Service Technicians; the Operative Plasterers’ and Cement Masons’ International Association; the International Union of Elevator Constructors; and the United Union of Roofers, Waterproofers, & Allied Workers.

A spokesman for the AFL-CIO declined to comment.

At issue is a new super PAC called For Our Future that Steyer, a former hedge fund manager, is financing in conjunction with the AFL-CIO; the American Federation of State, County and Municipal Employees; the American Federation of Teachers; and the National Education Association. As part of the partnership, Steyer has agreed to match the donations that the unions put into the group, helping amplify labor's resources. The organization plans to mobilize voters in key Senate races and presidential battleground states, and will be run by veteran Democratic strategist Paul Tewes, Politico reported. Tewes, who was a top political director for President Obama's 2008 campaign, has done work for All Risk, No Reward, an alliance of anti-Keystone groups.

Representatives of For Our Future did not have any immediate comment.

In a statement, Sky Gallegos, executive vice president of political strategy for Steyer's super PAC NextGen Climate, said that the group is "committed to preventing climate disaster and promoting prosperity for every American and that is precisely what our partnership with For Our Future aims to do. Our new unified effort will help elect progressive leaders who are committed to a just transition to a clean energy economy that will benefit working families across the nation.”

In their joint letter, the building trade union leaders said they would not contribute to For Our Future, and they called on the AFL-CIO to rethink the partnership.

Terry O'Sullivan, general president of the laborers' union, went even further in a separate letter to Trumka, accusing the labor federation of selling its political agenda to "a job-killing hedge fund manager with a bag of cash."

"This Super PAC creates a significant conflict between the interests of hard-working union members and the interests of those running the Super PAC," he wrote.

"With your blessing and support, Tom Steyer has purchased the backing, prestige, and control of the AFL-CIO, and will now use it to advance his own agenda, promote his own views, and further his own political ambitions," he wrote. "This scheme is the logical outcome of an obsession with, and a desire to throw open the doors of labor to, outside organizations that are completely out of touch with the needs and concerns of ordinary, blue-collar working Americans."

President Obama announced that his administration is rejecting the Keystone XL pipeline, as Secretary of State John Kerry and Vice President Biden looked on. (AP)