A key U.S. Senator is urging the Justice Department to take Yahoo! to the cleaners over its deal with Google.

Wisconsin Democrat Herb Kohl, Chairman of the Senate Judiciary Anti-trust Subcommittee, said his panel concluded that "important competition issues are raised by this transaction." He called on the DoJ to "continue to monitor the state of competition in this industry."

The DoJ is already examining the deal to decide whether to intervene, and had no comment Thursday beyond reiterating that the review continues.

Kohl urged the Justice Department to step in to protect competition if it determines that Google is "gaining a dominant market position" because of the agreement.