Under the card-check approach, employers must recognize unions once a majority of workers sign authorization cards saying they want to organize.

According to The Washington Post, the bill would "represent one of the most significant revisions of federal labor law in 60 years. It is the top legislative priority of the labor movement, which represents a record low 12 percent of the workforce, compared with 35 percent in the 1950s."

Many business organizations have spoken against the bill, including the U.S. Chamber of Commerce and the National Federation of Independent Businesses.

In a Feb. 13 letter to House Committee on Education and Labor Chairman George Miller, the U.S. Chamber of Commerce said that "unions are emphasizing the card-check process in their organizing drives, not because they do not win secret ballot elections – they win over 50 percent – but because it eliminates any chance of losing. As an open-ended process, they can keep a campaign going as long as necessary rather than resolve the issue on a specific date as with an election."

After passage of the bill in the House, the NFIB stated that "this legislation eliminates the democratic process of a secret ballot, which protects both small-business owners and their employees from intimidation, misinformation and exclusion from the very discussions that would affect their business. We find it disheartening that small businesses are being unfairly targeted by unions in a last-ditch effort to reverse the trends of their decreasing membership.

"One of the most troublesome provisions mandates compulsory, binding arbitration – this would have a devastating impact on small businesses."

Proponents of the legislation say the current system is skewed toward employers and does not protect workers' rights anymore. They say the bill will protect workers who support unions from being harassed or fired by employers determined to keep unions out of their businesses.

The AFL-CIO's blog says the bill would "strengthen America’s middle class by ensuring that workers who want to form unions and bargain for better wages, benefits and working conditions can do so without employer harassment."

AFL-CIO rallys highlighted workers who were fired during union-organizing campaigns and who waited years to get their jobs back or receive back pay, The Post said.

House Speaker Nancy Pelosi said, "The Employee Free Choice Act puts democracy back in the workplace so the decision to join a union can be made by the workers the union would represent. This is the standard right that we routinely demand for workers around the world. We should accept no less a standard here in America."

The bill is now in the Senate, where Republicans said they will filibuster. President Bush said he will veto the legislation if it reaches his desk.