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If Democratic leaders were trying to bring national attention to migrant farm labor by inviting comedian Stephen Colbert to a House panel hearing on Friday, they appear to have succeeded, but Colbert's performance didn't leave many lawmakers laughing.

"There was no rational reason for him to be there," Rep. Steve King, R-Iowa, told Fox News, adding that Colbert's joke-filled testimony didn't stick to the written testimony he had submitted Thursday night. Lawmakers expected him to summarize his points in five minutes, but he went longer -- and lacked substance, said King, a member of the panel.

"He went off on a comedy routine that he had written as a separate document and I think it's an insult to the time, an insult to the intelligence of the American people that Congress is conducting themselves in this fashion," King said.

Rep. Dan Lungren, R-Calif., acknowledged to FoxNews.com that he was thankful that Colbert's appearance brought publicity to an issue that Lungren's been working on for 37 years: "The contrast and comparison between unemployment of American citizens or nationals with the right to be in the U.S. and those here illegally."

But Lungren added that he would not want to see an encore.

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"I don't want to see this as a precedent because we have serious business here," said Lungren, also a member of the Judiciary Committee subcommittee that held the hearing.

Rep. Zoe Lofgren, D-Calif., chairwoman of the subcommittee, invited Colbert to speak at the hearing after the Comedy Central host spent a day picking beans alongside illegal immigrants as a guest of the United Farm Workers.

Colbert unleashed a monologue full of zingers and one-liners as he stayed in character as a blowhard conservative commentator for most of the testimony.

"This is America," Colbert said. "I don't want a tomato picked by a Mexican. I want it picked by an American, then sliced by a Guatemalan and served by a Venezuelan in a spa where a Chilean gives me a Brazilian."

After his day on the farm, Colbert said, "I don't even want to watch 'Green Acres' again."

He turned serious at the end of his testimony when he said he was using his star power to bring attention to farm labor because "these seem to be the least of my brothers."

"Right now, migrant workers suffer and have no rights," he said.

When contacted by FoxNews.com for reaction to Colbert's testimony, Lofgren's spokesman, Pedro Riverio, said she had no comment, preferring to let the hearing speak for itself.

"A little bit of humor always helps," Lungren said. "But if you try to make it into a humorous event, you miss the mark." He noted the high unemployment rate, especially in the minority communities. "It's no joking matter. That's why I hope people out there who don't have jobs who are struggling don't look us and think Congress doesn't take this seriously. I do and I think most of my colleagues do too."

But House Speaker Nancy Pelosi didn't think Colbert was out of line.

"Of course I think it's appropriate," she said. "He's an American. He can bring attention to an important issue. I think it's great."

Colbert faced a tough audience even before his testimony.

Rep. Lamar Smith, the ranking GOP member on the committee, recalled an episode of the "The Colbert Report," when the comedian debated himself on the issue and concluded that because he's an American TV host, his job is safe.

"Millions of Americans wish they didn't have to compete with cheap foreign labor and had such a safe job," Smith said. "Unfortunately, 17 million American workers are out of a job or have given up looking for work. It's no laughing matter to pretend that Americans don't want jobs. Pay them more if needed. But don't insult American workers by telling them the government cares more about illegal workers than U.S. citizens."

Rep. John Conyers, D-Mich, chairman of the committee, tried to kick Colbert out before he could testify.

"I'm asking you to leave the committee room completely, and submit your statement," he said.

But Colbert said he would only leave at the request of Lofgren.

"I'm here at the invitation of the chairwoman, and if she would like me to remove myself from the hearing room, I am happy to do so," he said.

Conyers later withdrew his request.