Wal-Mart: the High Cost of Low Price (PG) <!-- none onestar twostar threestar fourstar fivestar -->

Robert Greenwald's aim is to do for Wal-Mart - America's, and therefore the world's, largest retailer - something approaching what Morgan Spurlock did for McDonald's in Supersize Me, but he doesn't bring a quarter of Spurlock's energy and sheer sense of fun to this documentary. The basic charges levelled against Wal-Mart are familiar: that it underpays its workers quite shockingly, in effect using America's welfare system to subsidise its pay-roll; that it is discriminatory, offering almost no prospects of promotion to women or workers from ethnic minorities; and that it uses predatory practices to drive small shops out of business. And all this, by the way, is coming here, courtesy of Wal-Mart's takeover of Asda.

The film works best when Greenwald manages to contrast Wal-Mart's high-minded claims of social responsibility with its actual achievements, as when adverts with the slogan "Bringing it home to the USA", insisting on the importance of goods made in America, are juxtaposed with footage of the factories Wal-Mart runs in China. Elsewhere, though, Greenwald is maddeningly unspecific about Wal-Mart's alleged crimes. At one point, a caption says: "Wal-Mart drives down retail wages $3bn every year." Does that even mean anything? And while we hear a lot from small shopkeepers about how much they love their businesses and how much damage a local Wal-Mart is doing them, opening a big shop and selling stuff cheaper than the competition isn't unfair - it's just plain old capitalism, and you should never expect that to be fun.