The supermarket and petrol supplier which introduced the ban across Ireland a year ago, is extending its ban to two small towns in Waterford which, it claims, should not be exempt.

The move comes as increasing numbers of consumers are bulk-buying the vegetable oil to top up their car tanks as the price of petrol soars.

Residents of Lisduggan and Ardkeen will now be limited to buying nine litres of vegetable oil at a time.

One litre of vegetable oil in Tesco will set them back around €1, compared with €1.30 for a litre of petrol at the pumps outside.

The ban extension has angered consumer groups which claim customers should retain the choice to purchase what they want.

"We strongly oppose this move by Tesco. By limiting the number of items a customer can buy, Tesco are indirectly introducing price control, which is banned in Ireland," says Dermot Jewell, CEO of the Consumers Association of Ireland.

A Tesco spokesman defended their decision, claiming a ban on bulk purchases ensures that all customers get equal access to offers.