US supermarket giant Wal-Mart has used aggressive tactics, some illegal, to prevent staff from forming a union, a human rights group alleges.
In a report titled "Discounting Rights: Wal-Mart's violation of US workers' right to freedom of association", Human Rights Watch claims that the retailer uses a number of anti-union tactics and some "run afoul of soft US laws".
The report claims to have evidence that Wal-Mart, which employs 1.3 un-unionised staff in the US, "indoctrinates workers and managers to oppose unions from the moment they are hired".
Information in the firm's "manager's toolbox" reportedly gives instructions on how to "remain union free in the event union organisers choose your facility as their next target".
"Wal-Mart workers have virtually no chance to organise because they're up against unfair US labour laws and a giant company that will do just about anything to keep unions out," said Carol Pier, senior researcher on labour rights and trade for Human Rights Watch.
"That one-two punch devastates workers' right to form and join unions."
However the claims have been vehemently denied by Wal-Mart, the world's largest corporation which revealed profits of $11.3 billion (£5.64 billion) in 2006.
"Wal-Mart provides an environment of open communications and gives our associates every opportunity to express their ideas, comments and concerns," a spokesperson for Wal-Mart, David Tovar, said.
"It is because of our efforts to foster such an environment that our associates have repeatedly rejected unionisation attempts."