US comedian Stephen Colbert makes light work of the lot of illegal labourers

• Joker in the pack: Comedian Stephen Colbert, in TV show pose below, testified in character to the House committee Picture: Getty

Mr Colbert, who hosts the Colbert Report show on the Comedy Central channel, was testifying to the immigration subcommittee hearing evidence on the plight on illegal farmworkers.

He told the committee that one day picking beans alongside illegal immigrants had convinced him that farm work is "really, really hard."

"It turns out - and I did not know this - most soil is at ground level," he testified. He added: "It was hotter than I like to be."

However, true to his slightly zany humour, Mr Colbert expressed bemusement that more Americans were not clamouring to "begin an exciting career" in the fields and instead were leaving the dirty work to illegal immigrants.

Mr Colbert offered the House hearing his "vast" knowledge, drawn from spending that single day on a New York farm as a guest of the United Farm Workers union.

The union recently launched its "Take Our Jobs" campaign in an attempt to back up claims that few Americans want to do the labouring done by farm workers, the vast majority of whom are not legally in the country. Only seven people accepted the advertised jobs, the union said. Mr Colbert pleaded with the committee to do something about the use of workers illegally in the country, because "I am not going back out there."

After praising him for drawing an unusually large audience to the immigration subcommittee hearing, House judiciary chairman John Conyers asked the comedian to leave the room - and to leave the job of testifying to the expert witnesses on the panel, including Farm Workers president Arturo Rodriguez.

"You run your show, we run the committee," said Democrat Mr Conyers.

There had been some complaints about Mr Colbert testifying in character at the hearing. Other celebrities have testified as themselves. But Congress has heard testimony from the Sesame Street puppet Elmo over music education for children.

Earlier Mr Colbert told Mr Conyers that he was there at the invitation of Democratic subcommittee chairwoman Zoe Lofgren to discuss his experience as an American who did the work of a farm labourer.

After being given permission to testify, Mr Colbert wiped his brow and launched into his act, insisting he wanted his tomatoes picked by Americans, not Mexicans; "sliced by a Guatemalan and served by a Venezuelan in a spa where a Chilean gives me a Brazilian."

"I'm not a fan of the government doing anything," he insisted.

"But I've got to ask, Why isn't the government doing anything" about the fact that its agricultural industry depends on immigrant labour.

Officials estimates that between 60 to 75 per cent of farm workers are illegal immigrants.

Mr Colbert's humour drew guffaws from public galleries and several of the Democrats on the committee. Most of the Republicans sat silent and unsmiling as he delivered his punchlines. "Maybe we should be spending less time watching Comedy Central and more time considering all the real jobs that are out there," said Republican Steve King.

Republican Lamar Smith's eyes lit up, however, when Mr Colbert said more Americans may take farm worker jobs because many Democrats may be looking for work in November, after the mid-term elections.

Mr Colbert turned serious at the close of the hearing. He said he chose to use his celebrity to bring attention to farm labour because "these seem to be the least of my brothers." "Right now migrant workers suffer and have no rights," he said.