McDonald's, the world's biggest fast-food chain, says sales in Australia are going backwards, citing incorrect figures on the level of youth unemployment to help explain why fewer people are buying its burgers and fries.

Although the introduction of the "Loose Change" menu in 2012 bolstered sales of its food last year, thrifty consumers have withdrawn from even that bargain basement offer and are spending less at the McDonald's counter.

Addressing investors in the US, McDonald's global chief executive and president Don Thompson warned that lower levels of spending in Australia and cut-throat competition among fast-food chains in the region had slashed revenue for the company.

He told the mostly US audience that the economy in Australia had worsened since 2012 and is reported to have said that youth unemployment had hit more than 25 per cent.