Tensions between Virginia Gov. Bob McDonnell and the board overseeing construction of the $6 billion Dulles rail project escalated this week when McDonnell ordered that a union official be removed from the board.

McDonnell ordered the removal of Dennis Martire, a vice president of Labors’ International Union of North America and an appointee of former Democractic Gov. Tim Kaine, from the Metropolitan Washington Airports Authority board. Martire filed a lawsuit in U.S. District Court Thursday to fight the order.

McDonnell’s office alleged that Martire’s union affiliation created a conflict of interest in rail line decisions and that Martire's recently well-publicized taxpayer-funded travel — including a $9,000 flight to Prague — were reason to remove him from the board.

Martire’s expenses came to light in a recent federal inspector general’s report that slammed the authority for questionable contracting practices, lax ethics policies and wasteful spending.

In his lawsuit, Martire the governor’s move was “unlawful and politically-motivated.”

“I believe there is no cause to justify my removal. I take my responsibilities as a board member very seriously,” Martire wrote in a letter to McDonnell’s chief of staff. “I never violated any rules, and my behavior was consistent with that of other board and staff members.”

Martire said he followed all the board’s travel policies and that a lawyer for the airports authority had determined his union job did not constitute a conflict of interest. Virginia officials and the airports authority have been at odds for months over the use of union labor on the rail project. McDonnell threatened to withhold state financing for the project unless the board backed off its insistence on a union-friendly labor agreement. The board ultimately backed down.

The airports authority portrayed McDonnell's call for Matire's ouster an unprecedented attack on its board.

“The removal of a sitting board member whose term has not expired is an unprecedented act,” the airports authority said in a statement. “The board and senior staff will review the governor's letter and consult with legal counsel before responding to the governor’s action.”

The board resisted McDonnell before on a personnel matter, refusing to seat his two new appointees until both Virginia and D.C. ratified federal changes to an interstate compact.