Allegations of wrongdoing against one of labor’s strongest voices could undermine efforts to take up the Employee Free Choice Act during the first 100 days of the Obama administration, according to sources on both sides of the issue.

Labor unions have made passage of the Free Choice Act their top priority during the 111th Congress, but a growing number of allegations against the Service Employees International Union — in particular its relationship with Illinois Gov. Rod Blagojevich — have called into question whether Congress and the Obama administration would be willing to move the bill early on.

The SEIU is one of the fastest growing unions in the country, representing the health care, property and public services sectors. Blagojevich was arrested on Dec. 9 for allegedly seeking favors from the Obama administration and others — including SEIU — in exchange for a say in his appointment of Obama’s vacant Senate seat.

According to the Justice Department complaint, an SEIU official listened to and agreed to consider Blagojevich’s proposal to trade the Senate appointment for a high-paying job with the union.

The complaint, said the Center for Union Fact’s executive director Richard Berman, “has shone a light on SEIU’s propensity for doing business with corrupt groups and people.”

SEIU spokeswoman Michelle Ringuette argues that no one in the union has been accused of any wrongdoing; that simply being mentioned in a criminal complaint is not tantamount to guilt. And she said the union has made every effort to cooperate with the federal government in its case against the governor.

The legislation would eliminate secret-ballot elections, instead allowing a union bargaining unit to be formed as soon as a majority of workers signed authorization cards. It also mandates arbitration if contract negotiations stall and imposes penalties on employers that coerce workers not to join unions. A manufacturing business official described this bill as a “deal breaker” that would end any honeymoon between the Obama administration and Republicans.

A House GOP aide agreed that the charges would have an impact. The legislation is “going to be looked at with a much more critical eye in light of these allegations,” said the GOP aide.

But an aide to Education and Labor Chairman George Miller (D-Calif.), the bill1’s House sponsor, rejected these arguments.

“After eight years of a disastrous Bush administration, nothing will stop us from enacting measures to help workers fight for their economic security like access to healthcare, safe working conditions and sharing in improved productivity,” the aide said in an e-mailed statement.

The bill’s passage is also sure to receive a boost from President-elect Barack Obama’s choice of Rep. Hilda Solis (D-Calif.) as Labor secretary. Solis was an original co-sponsor of the Employee Free Choice Act and carries a 97 percent lifetime rating from the AFL-CIO.

Last year the bill passed overwhelmingly in the House, but fell in the Senate when Democrats failed to gain the sixty votes needed to cut off debate and hold a straight up or down vote