WASHINGTON | Scrutiny over U.S. Rep. Pete Visclosky's ties to a disgraced lobbying firm intensified Thursday as a Republican colleague urged his ouster from the high-powered House Appropriations Committee.

Rep. Darrell Issa asked fellow Californian and Democratic House Speaker Nancy Pelosi to urge Visclosky to resign from the committee pending the outcome of the federal probe into defunct firm The PMA Group.

MORE: Read a news release from U.S. Rep. Darrell Issa, R-Calf., asking House Speaker Nancy Pelosi to urge Rep. Pete Visclosky to resign from the Committee on Appropriations pending the outcome of an ongoing federal investigation into his congressional and campaign activities.

"Now that federal law enforcement officials have ratcheted up their highly public probe of Rep. Visclosky, he must resign immediately from the Committee on Appropriations," Issa, a ranking minority member of the House oversight committee, wrote to Pelosi.

Pelosi spokesman Brendan Daly said Thursday the speaker will not ask Visclosky to resign.

Visclosky had no comment Thursday regarding Issa's request, his spokesman Jacob Ritvo said.

Visclosky announced last week his office, campaign committees and some employees have been sent grand jury subpoenas requesting documents relating to PMA.

MORE: Read previous stories about PMA and Pete Visclosky.

In November, the FBI raided the Virginia-based firm, which for years had been the top source of Visclosky's campaign cash.

Since 1998, the firm and its clients -- through political action committees or employees and their families -- contributed nearly $1.38 million to Visclosky, according to the Center for Responsive Politics.

Visclosky's colleague on the appropriations as well as the Energy and Water Subcommittee, Rep. John Murtha, D-Pa., also has been embroiled in the PMA controversy as a top recipient of the firm's donations.

Issa spokesman Kurt Bardella said Issa is not pushing for Murtha's removal from the appropriations panel because Murtha has not been publicly targeted by the FBI.

As chairman of the Energy and Water Subcommittee, Visclosky is one of the so-called cardinals of the Congress who control federal spending.

Earlier this week, Visclosky ceded his control over the 2010 energy and water spending bill, saying he wanted to deflect any Republican attempt to use the PMA case to disrupt the appropriations process.

Issa called Visclosky's decision "entirely insufficient given the grave nature of the controversy surrounding him."

According to Larry Baas, chairman of Valparaiso University's political science department, Issa's resignation request is likely the kind of political grandstanding Visclosky wanted to prevent.

"This seems to be a means of changing the attention," Baas said. "Politics has become loaded with these spectacles, series of dramas."