"Always low prices" is the endlessly repeated corporate slogan of Wal-Mart, the world's biggest retailer. But now, if the price of an item is low enough - under $25 (£13.50) - you might get away without paying at all.

The chain has decided to stop seeking prosecution of shoplifters stealing goods worth less than $25, ending a long-standing "zero tolerance" policy inaugurated by the firm's strictly moral founder, Sam Walton.

Shoplifters under 18 or over 64 will also escape prosecution, according to an internal memo leaked to the New York Times by an anti-Wal-Mart pressure group. The store will continue to seek prosecution of all suspected thieves who threaten violence or refuse to show identification.

The previous policy of prosecuting any thefts over $3 had overstretched local police departments, some of which were forced to hire extra officers to attend to Wal-Mart's calls. It also brings the company into line with most of its rivals, and frees up resources for fighting the bigger problems of organised shoplifting and theft by members of Wal-Mart's own 1.3 million workforce.

"If I have somebody being paid $12 an hour processing a $5 theft, I have just lost money," JP Suarez, the company's head of asset protection, told the New York Times. "I have also lost the time to catch somebody stealing $100 or an organised group stealing $3,000."