After 16 years as president of the National Treasury Employees Union (NTEU), Colleen M. Kelley gave her farewell speech Monday, saying “the past few years will rank among some of the most difficult in the history of the federal workforce.”

Colleen M. Kelley (National Treasury Employees Union )

The future also will be difficult for the union if Senate Republicans get their way. Republicans on the Senate Finance Committee want to prohibit union membership for employees in the Internal Revenue Service (IRS), which is NTEU’s base.

Before retiring Thursday, Kelley gave her final NTEU State of the Union speech at the labor organization’s convention in Hollywood, Fla.

She recalled a number of NTEU victories during her tenure, among them organizing workers at several federal agencies, including a particularly tough campaign at the Securities and Exchange Commission.

[Read Colleen Kelley’s farewell speech]

“The SEC fought us tooth and nail,” she said. “They agreed to an election, then reneged. The FLRA (Federal Labor Relations Authority) ordered an election; SEC appealed. We held a very visible rally and, finally, an election, and of course, we won.”

Another big battle looms if the Republican proposal to ban unions from the IRS advances.

The “Additional Republican Views” section of a Senate Finance Committee report released last week takes aim directly at NTEU and Kelley. The report examines accusations of political bias at the IRS.

[Read the “Additional Republican Views“]

“It is virtually impossible for the IRS to maintain the reality, much less the appearance, of neutrality and fairness to all taxpayers, when a substantial number of IRS employees are members of the highly partisan and left-leaning National Treasury Employees Union,” the report says. The Republican views were previously reported by Government Executive.

About Kelley, the report notes that she “is now both union president and an Obama administration appointee to the Federal Salary Council, whose function is to recommend raises for IRS and other federal employees. During the 2010 election cycle, when the IRS targeting of Tea Party groups began, the NTEU raised $613,633 through its political action committee (PAC), donating approximately 98% of that amount to Democrats. In 2012, $729,708 – or 94% of NTEU PAC contributions – went to anti-Tea Party Democrats.”

The Republicans said the law “must be amended to designate the IRS as an agency that is exempt from labor organization and collective bargaining requirements.”

Democrats on the committee responded by saying “Union membership in and of itself does not mean political bias. The Additional Republican Views establish no factual evidence that any IRS employee, whether they belonged to a union or not, was politically biased in their actions related to the 501(c)(4) applications with political advocacy issues.”

Furthermore, the Democrats pointed out that Lois Lerner, the IRS executive at the center of the IRS controversy, was not eligible for union membership.