Hashem Al-Nuaimi, head of consumer protection department at the Ministry of Economy, said the companies reduced the can size without prior approval from the government. He said Coca Cola has violated government rules by reducing the size of their cans from 355ml to 300ml but selling at the same price of Dh1.5 in retail stores.

"We took this measure against the two companies after we had received public complaints in this regard," Al-Nuaimi said.

A source at Dubai Refreshments, the exclusive distributor of Pepsi in Dubai and the Northern Emirates, said they only sold the 300 ml cans to tourism firms and retail outlets selling the cans had not bought directly from the company. However, 300 ml Pepsi bottles were available at supermarkets and hypermarkets on Monday.

"We don't know the new move and we don't have instructions to remove it from our shelf," a supermarket supervisor in Sharjah said.

Coca-Cola and Pepsi had raised prices by 50 per cent during the first week of January  2011. That was the first price-rise during the last 20 years.