Unions are to blame for the Big Three automakers’ problems, according to a television ad meant to stoke public opposition to organized labor’s number one legislative priority.

“Steel, auto, airlines. What do these industries all have in common?” asks the ad sponsored by the business-backed Employee Freedom Action Committee, which was active in several hotly contested Senate races this year. “Hundreds of thousands of lost jobs and union bosses that helped put them out of business.”

Business groups are paying for the ad to run on CNN and the Fox cable news network Monday through Wednesday, according to the group’s spokesman, Tim Miller. He said the ad buy was “fairly substantial” but declined to specify a figure. A similar ad ran in Mississippi and New Hampshire in conjunction with Senate races in those states, where business groups worked to tie Democrats to the Employee Free Choice Act.

“If Americans like what the unions did to Detroit’s economy, they’ll love what the unions will do to the country,” said Richard Berman, the business group’s executive director.

“The unions have played a significant role in nearly bankrupting the Big Three automakers with untenable inefficiencies which have put tens of thousands out of work,” Bergman said. He said the union bill, known as “card-check legislation,” would do the same to millions of jobs across the country.

Alan Reuther, legislative director for the United Autoworkers, blasted the ad and Bergman’s comments. He said the auto industry’s problems rest on a series of bad trade and healthcare policies, and that the credit crunch is to blame for the current crisis.

Reuther also said major concessions offered by unions in their 2005 and 2007 contracts will result in the elimination of the cost-gap between union and non-union plants. “We feel that we’ve stepped up to the plate,” he said.

He also pointed to a 2007 report by two auto industry consulting firms that found nine of the 10 most-efficient auto plants in North America have workers organized by the United Autoworkers or the Canadian Autoworkers.

Congressional leaders have asked the cash-strapped auto companies to come up with a business plan over the next two weeks if they want $25 billion in aid. Executives from the three companies were in Washington this week pleading for help.

Besides arguing that it would slow the economy, the U.S. Chamber of Commerce, National Association of Manufacturers and other business groups warn that card-check would let union bosses intimidate workers into forming unions.

Labor groups charge that the current system allows employers to use intimidation tactics to stop workers from organizing. Allowing workers to form unions by checking cards authorizing a specific union to represent them ­ rather than casting secret ballots would solve the problem, they say.

Separately, a coalition of business groups wrote to members of Congress urging that they not sign on to card-check legislation.

“Particularly at a time of economic uncertainty, Congress should not enact measures that threaten our economic competitiveness, including the Employee Free Choice Act,” stated the letter, which was signed by dozens of business groups.