The claims could put further pressure on the country's meat processors to step up to the food safety mark, as US lawmakers are now cracking down on food safety plants across the country.

The latest report was compiled by the United Food and Commercial Workers union (UFCW) from Food Safety and Inspection Service (FSIS) documents, and details a number of food safety incidences that allegedly took place at Agriprocessors' Nebraska plant between 2005 and 2007.

According to the union, the company failed separate specified risk material (SRM) such as the spinal cord from meat products, "including one occasion in which products containing SRM was labelled, weighed and taped shut."

The plant was also accused of transmitting the E. coli bacteria, a pathogen that can cause severe human food poisoning, through its meat. The report claims that the firm improperly tested for the bacteria on a number of occasions, leading to a non-compliance (NR) record being issued in March 2007.

The report claims in addition that the firm failed to comply with over 20 hazard analysis and critical control point (HACCP) controls - rules that are a systematic preventative approach to food safety aiming to spot hazards during the manufacturing process - and operated its plant in an unsanitary manner.

For example, FSIS found "overwhelming fly populations" in the plant, and stated that the plumbing system was inadequate to convey sewage and waste.

The company was issued with more than 115 non-compliance records in total, the report states.

However, Agriprocessors vice president Sholom Rubashkin told Forbes news agency that the union's allegations were an attempt to hurt the business as the workers have voted against unionizing for the past three years.

"The union is not the authority for wholesomeness," he said. "All they are tying to do is make these allegations to dirty someone's name and hurt commerce."