PORTLAND, Maine (AP) — U.S. Reps. Tom Allen of Maine and Henry Waxman of California are trading accusations with Sen. Susan Collins over contractor fraud in Iraq as the Senate race heats up.

The two Democrats say Collins failed when she was Republican chairwoman of the Senate Committee on Homeland Security and Governmental Affairs to do anything about $23 billion in waste, abuse and fraud. Waxman criticized Collins as “absent without leave.”

But a spokesman for Collins says she did hold a hearing on contractor abuse, and that her efforts helped to prevent the elimination of an independent auditor who briefed her committee 12 times.

Waxman and Collins are at odds over competing versions of a bill that would address contractor fraud. Collins sponsored the Senate version. The stalemate in conference committee focuses on contractor whistleblower and no-bid contracts for Native Americans.