The world's biggest retailer, Wal-Mart, today stands accused of routinely flouting its workers' human rights through a sophisticated strategy of harassing union organisers, discriminating against long-term staff and indoctrinating employees with misleading propaganda.

In a forensic indictment based on two years' research, the Washington-based pressure group Human Rights Watch lifts the lid on Wal-Mart's aggressive tactic of stamping on the slightest sign that workers are organising representation.

Evidence in Discounting Rights includes examples of workers forced into unpaid overtime and an alleged strategy of squeezing out long-serving staff who are more costly than low-wage, temporary, younger workers.

It reveals that Wal-Mart, which owns Britain's Asda, has elaborate tactics to stop staff from coming together to fight for better conditions. The company is accused of focusing security cameras on areas where staff congregate and shifting around loyal workers in "unit packing" tactics to ensure votes for union recognition are defeated.

American store bosses get a "manager's toolbox" - a manual which openly describes itself as a guide on "how to remain free in the event union organisers choose your facility as their next target".

They are told to phone a special "union hotline" if they suspect staff. Teams of union busters are then sent from Wal-Mart's Arkansas headquarters who regale workers with vitriolic presentations on the perils of unionisation.

Carol Price, author of the report, said: "Wal-Mart's aggressive and sophisticated anti-union strategy is based out of its headquarters. This is not a store-by-store problem - the violations are a direct result of the company's philosophy."

With $351bn (£176bn) in annual revenue and 1.8m staff worldwide, Wal-Mart was named America's largest company in the latest Fortune 500 rankings but its controversial business practices have caused increasing political unease. Unions organised a nationwide protest bus tour last year and prominent politicians have been getting on board.

The Norwegian government has ordered its state pension fund not to invest in Wal-Mart shares because of workers' rights violations. Hillary Clinton last week pointedly refused to endorse the company when asked during a presidential debate whether she considered it to be good or bad for America.

"It's a mixed blessing," Mrs Clinton said. Although Wal-Mart provides many jobs in rundown areas of her former home state of Arkansas, she said its behaviour raises "serious questions about the responsibility of corporations" in providing healthcare, safe working conditions and an environment of equality.

Combining documentary evidence with interviews of dozens of past and present Wal-Mart employees, Human Rights Watch has built a picture of a company which goes to great lengths to minimise the freedom of its staff.

Healthcare programmes are often limited to "catastrophic coverage" for accidents and emergencies, rather than preventative medicines. The company faces the biggest class action lawsuit in US history in which 1.5m women claim the company discriminated against female staff in pay, promotions and assignments.

In a breach of US law, Wal-Mart has allegedly banned union organisers from distributing flyers outside its stores and has confiscated literature found on the premises. Since Wal-Mart began in 1962, there has only been one successful formation of a union - among meat cutters in Texas seven years ago. The department was subsequently shut down - an act ruled illegal by US labour authorities.

Faced with increasingly vocal opposition, Wal-Mart's chief executive, Lee Scott, has been trying to improve the company's image. It has introduced more upmarket items and is testing environmentally friendly initiatives at two experimental green stores. Mr Scott has pledged to improve healthcare coverage and, in a significant breakthrough, he held a meeting in February with one of the company's most outspoken critics - Andy Stern, the head of the Service Employees International Union. The company has even distributed voting information to all its 1.3m US staff encouraging them to register for a voice at the next presidential election.

Wal-Mart had not responded to repeated requests for comment by the time the Guardian went to press last night.



Film campaign



Need to bash a union? A video production company discreetly tucked away in a 113-year-old former general store in America's rural deep south can help.

Paul French & Partners specialises in making bespoke, glossy films dramatising the so-called impact of union recognition - strikes, redundancies and uncompetitive, failing businesses.

Wal-Mart uses Paul French to produce films ostensibly to explain "the facts" to workers about union membership. But the Georgia-based firm's website makes no bones about its true purpose - to prevent union recruitment drives.

A sample film made for a valves company, DeZurik, is ironically entitled "It couldn't happen here" and bombards the viewer with examples of disruptive strikes by unions.

Another, for Delta Mechanics, depicts organisers as silky-tongued manipulators who pressurise staff around the clock until they join.

A third film for Allied Holdings dramatises the pain of redundancies caused when union-negotiated pay rises make a company uncompetitive.

When contacted by phone, the firm's founder, Paul French, was reluctant to talk about such films: "A small number of our pieces are on that subject. I would rather talk to you about [films on] sexual harassment and violence in the workplace."

When asked whether he had any qualms about union-bashing films, Mr French simply said: "No".

Paul French boasts a blue-chip client list including General Electric, Fruit of the Loom, Lockheed Martin and Wrangler, although the type of work it carries out is not disclosed.

Persuasive videos are a relatively common tactic for employers in America - the Scottish bus company FirstGroup recently angered the mighty Teamsters union by using videos to "inform" its US staff about the impact of signing up.