Ajemex has come under attack from Mexican union leaders requesting a government investigation into the company. Fifty-three regional union leaders signed a full-page advertisement in El Independiente newspaper on Wednesday, asking officials to examine labour and commercial practices at the Mexican unit of Peruvian beverage group Kola Real.

The unions are unhappy at Ajemex's arrangements with distributors. While many of the large bottlers in Mexico have distributors on their payrolls and subsequently pay the distributors' taxes and retirement benefits, Ajemex outsources distribution to individual truckers. The regional union leaders accused Ajemex of failing to contribute to health, housing and pension plans on behalf of its workers, as required by Mexican law.

Ajemex, which makes the popular bargain-brand Big Cola, acknowledged that it has contracts with hundreds of individual truckers, but said that the practice was totally legal.

Mexico has the highest soda per capita consumption in the world. Since arriving in the country two years ago, Big Cola has taken 5% of Mexico's drink market.