Attorney General Eric Holder vigorously denied a "cover-up" by the Justice Department over "Operation Fast and Furious," telling a House panel investigating the botched gun-running program that he has nothing to hide and suggesting the probe is a "political" effort to embarrass the administration.

"There's no attempt at any kind of cover-up," Holder told lawmakers well into a hearing about whether he had been forthright in responding to requests of the House Oversight and Government Relations Committee led by Chairman Darrell Issa, R-Calif.

"We're not going to be hiding behind any kind of privileges or anything," he said.

The hearing came after Issa and Sen. Charles Grassley, R-Iowa, his Senate partner in the probe, asserted that top Justice officials are covering up events surrounding the flawed gun-smuggling probe. 

Issa made the accusation in a letter threatening to seek a contempt of Congress ruling against Holder for failing to turn over congressionally subpoenaed documents that were created after problems with Fast and Furious came to light.