The House Public Works and Transportation Committee said awful things about the Union Station-National Visitor Center yesterday and then authorized $39 million to complete renovation of the complex.

Rep. William H. Harsha (R-Ohio) called it "a blight on the community . . . practically useless." Rep. Ray Roberts (D-Tex.) said it was a "a mess . . . an eyesore . . . get it behind us."

The rationale for pouring still more money into the project- $45 million has been spent so far and the completed cost now is estimated to be about $106 million-was expressed by Rep. Elliott H. Levitas (D-Ga.), whose public buildings and ground subcommittee proposed the legislation.

"The problem is, it's there," said Levitas. "We must either finish it or leave it as a monument to how bad government can be."

"That might not be a bad idea," groused Snyder.

The legislation would provide money to complete a 1,400-parking garage, return the train depot to the main building, make needed repairs to the crumbling but classic Roman structure, and allow for resuming activities at the visitor center in the front.

The proposal still must face the full House (where Committee Chairman Harold T. Johnson said, "it's not going to be the easiest thing to sell,") and the Senate, and the respective appropriation committees of the two bodies.

The Kennedy Center did not get off much easier before the same committee yesterday.

Legislation was approved authorizing $4.2 million for fiscal 1980 to cover most of the costs of such nonperforming arts functions as maintenance, security, information and janitorial services.

"That management down there [at the center] leaves a lot to be desired," said Harsha, the ranking minority member of the committee. He said that until Congress stepped in seven years ago and put the Interior Department in the charge of appropriations, the financing was "a nightmare."

Because of cocerns about financing, Levitas amended the legislation to limit the appropriation to a single year.

Further action, including what to do about $15 million interest owed to the U.S. Treasury on bonds issued for construction, will be held back until the General Accounting Office completes a report on the center in August, Levitas said.