WOOLWORTHS has been cheating customers of its online store by displaying inaccurate unit prices for common grocery items.

Laws introduced last December require all major grocery chains to display prices for a common measurement for a product as well as the total price.

Supermarket online stores are also required to display unit prices, which are designed to help consumers compare similar items of varying sizes.

However, a Herald investigation of the Woolworths online shop found major discrepancies in the unit prices of many items. In one case, the actual unit price for a block of chocolate was 122 per cent higher than the unit price shown. Retailers caught breaching the unit pricing laws face penalties up to $1.1 million

A spokesman for Choice, Christopher Zinn, said it was unlikely the Australian Competition and Consumer Commission would prosecute Woolworths over the alleged breach.