"We are seeing little to no change at these plants," said Stan Painter, the union's chairman.

The USDA has said its ban on brains, spinal cord, eyes and other so-called specific risk material (SRMs) was the most important action it has taken since the discovery of mad cow disease in the United States.

The deadly disease is carried within the infected animal's brain and nervous system and can be spread to humans when eaten. Older cattle, over 30-months of age, are thought to be at higher risk for mad cow disease than younger animals.

"We know USDA's zero tolerance is not being met," Painter said. "We believe this is a widespread problem." He declined to say how many plants were in violation.

The USDA disagreed with the union, saying no prohibited cattle parts were slipping into the food supply.

"Parts that are defined as SRMs are being removed and being disposed of according to regulations implemented in January 2004," said Steve Cohen, spokesman for USDA's Food Safety and Inspection Service.

The American Meat Institute, a trade group representing US meatpackers, said it was unaware of any plants in violation of the regulations.

The labor union's allegations come as the United States tries to convince Japan and South Korea, previously its top buyers, to ease their bans on US beef.

Japan, the No. 1 market for US beef in 2003, said it would reopen its borders once Washington could assure that only beef from cattle 20 months or younger would be shipped.

"I would think (Japan) will definitely have a concern about this," Painter said.

SLIPPING THROUGH

In October, US meat inspectors began alerting the union that plant employees were incorrectly identifying carcasses of animals over 30 months old, Painter said. Under USDA procedures, plant employees are responsible for identifying older cattle by examining their teeth.

Painter said these violations allowed prohibited parts to slip by inspectors and enter the food supply.

Inspectors said plants were also violating a trade agreement with Mexico by shipping kidneys from cattle over 30 months old.

The union said inspectors were being told by their supervisors not to intervene when they noticed export requirements of Mexico were not being followed.

"We have seen cattle that have been over 30 months ... and the kidneys were shipped to Mexico," Painter said.

Painter said slaughter plants needed to segregate their production lines by age. The union also urged the USDA to give inspectors more authority to enforce regulations.