The UFCW yesterday filed a lawsuit in Texas claiming that immigration officials violated the law while conducting raids last December on Swift & Co plants in search for illegal workers.

Although illegal workers cost the food industry millions of dollars in fines and lost revenue every year, the government's tough stance is being slowed down because unions fear that the reforms infringe on workers' human rights.

In December 2006, about 12,000 workers at various Smith & Co meat factories were subject to raids carried out by the Immigration and Customs Enforcement (ICE) agency, after which 65 individuals were indicted for identity theft.

According to the UFCW, officials denied all of the workers at the plants access to telephones, bathrooms and legal counsel, while legal workers were not allowed to retrieve documents that proved their status.

However, by law US citizens have the right to be free from unreasonable searchers and seizures while at work, the UFCW added.

"This lawsuit is about ensuring that workers are protected and that their constitutional rights are respected," said UFCW president Joe Hansen at a press conference announcing the lawsuit. "It is unconscionable that our government would round up hundreds, sometimes thousands, of innocent workers in an effort to target a few select individuals."

The union will help workers to seek damages for the violation of their constitutional rights, Hansen said.

Immigration officials raided six Smith & Co last year as part of President George Bush's attempt at monitoring and eradicating illegal workers.

Government officials arrested around 1,300 workers during the raids, mainly immigrants from Mexico, which cost the company about $30m in lost production.

Other promised reforms include a temporary work permit system, increased fines against employers breaking the law and broader security.

According to Bush, the number of illegal workers caught at manufacturing sites has increased dramatically during his term in office. About 4,300 arrests were made in worksite enforcement cases during 2006, more than seven times the arrests in 2002.