The uproar over working conditions in America's largest kosher meat-processing plant reached Congress last week, as a dozen Jewish lawmakers sent a letter to the owners of Agriprocessors deploring the company's practices.

"The treatment of its workers and the animals raise serious questions about the company's compliance with US law and the highest standards of Jewish law and tradition concerning kashrut," the letter read.

Following a May raid by immigration enforcement officers on the meat-packing plant in Postville, Iowa, Agriprocessors came under the scrutiny of government agencies, as well as the Jewish community, regarding its treatment of employees - many of them undocumented aliens - as well as over their use of child labour, safety practices and inhumane treatment of animals.

Agriprocessors, trying to field criticism from all walks of Jewish life, appointed a new chief executive officer who is expected to correct practices and move the kosher meat processing giant away from its troubled image.

The Agriprocessors affair has moved Reform and Conservative movements in the US to stress the value of a "hecsher tzedek" which will add the need for fair treatment to the kosher certificate.

The Orthodox Union, which holds one of America's largest kashrut operations, threatened to pull its approval from Agriprocessors products if the company did not replace its leadership and correct flaws that were pointed out by the government, watchdog groups and the press. Agriprocessors has denied any wrongdoing.