Union bosses claim to be America’s worker advocates — fighting for coal miners and fast-food employees against Big Business. But 2016 union disclosure forms paint an entirely different picture.

According to the recently released financial reports of three major labor unions — the AFL-CIO, American Federation of Teachers and National Education Association — Big Labor spends huge sums of dues dollars on implicitly political advocacy far removed from worker advocacy.

Richard Trumka’s AFL-CIO sent nearly $700,000 to Catalist, a leading Democratic Party data firm founded by Harold Ickes — a former Hillary Clinton aide — and backed by George Soros. The AFL-CIO also donated about $338,000 to New Partners Consulting — a political consulting firm run by former Democratic Party officials — and more than $292,000 to the Pivot Group, a Democratic direct-mail firm. Even worse, the AFL-CIO classified a $108,480 payment to ShareProgress as a “representational activity.” Yet ShareProgress is a “progressive” technology firm serving the “political left.”

The country’s two largest teachers unions — the AFT and NEA — gladly joined the party. Randi Weingarten’s AFT sent $300,000 to the Philadelphia 2016 Host Committee — the organizer of the Democratic National Convention — and $500,000 total to the Clinton Foundation and Clinton Global Initiative. The left-wing Center for Popular Democracy received $373,000, while the pro-abortion Emily’s List made off with $125,000.

The NEA contributed an additional $627,000 to Catalist and $510,000 to the Philadelphia 2016 Host Committee. The New Media Firm, another Democratic consultancy, received a whopping $1.5 million from Lily Eskelsen Garcia’s teachers union this year.

This is nothing new. Center for Union Facts research shows that Big Labor sent nearly $530 million to Democrats and closely aligned liberal special interest groups from 2012 to 2015 — 99 percent of their entire advocacy budget. The Democratic Governors Association was a top beneficiary, raking in more than $10 million in a four-year span.

All of these line items fall on top of direct campaign and super PAC donations, which surpassed $160 million in 2016 and union members voluntarily support. Under current labor law, union leaders are not required to obtain prior approval before spending member dues on political advocacy.

This matters because roughly 40 percent of union members vote Republican in any given election cycle. In 2016, 43 percent of union household voters supported Donald Trump. The most recent NEA survey of public school teachers found that 55 percent of teachers characterize themselves as “conservative” or “tend to be conservative.”

Think about it this way: An employee represented by an AFL-CIO member union must explicitly object to donating dues dollars to the union’s advocacy budget. Current labor law makes political dues deductions the automatic default. And opting out is nearly impossible because union intimidation is all too common. When right-leaning union members are unable to opt out, then they are essentially forced to support the Clinton Foundation and other partisan groups.

That’s why the 115th Congress will likely reintroduce the Employee Rights Act, labor legislation meant to protect employees from unapproved political advocacy spending. The ERA would require union officials to obtain prior approval before sending member dues — still mandatory in non-right-to-work states — to the Clinton Foundations of the world. Unsurprisingly, the bill’s political protection clause registers more than 80 percent approval among union households.

The Employee Rights Act would hold union bosses — America’s self-proclaimed worker advocates — to their word.