Former cabinet minister John Denham is calling for all supermarkets to make prices available online so consumers can make accurate comparisons and monitor price changes and offers.

Supermarkets are not required to publish information on pricing, but Denham wants the Government to change this. He says all supermarkets should release pricing data in a standard, accessible format on the web.

Consumers can't shop online at Aldi, Lidl, Morrisons and the Co-op, meaning their prices aren't easily available online for shoppers to compare.

Website MySupermarket offers a comparison service for consumers, but does not include prices from those four retailers, mainly for those reasons.

Labour MP Denham wrote on the party's Policy Portal — a website used by senior MPs to create debate — that if supermarkets made pricing information available, organisations and individuals would be able to create price comparison tools to help consumers.

He says: "Supermarkets run sophisticated pricing policies, informed by detailed analysis of customer behaviour. This is a modest proposal that would help consumers exercise real, informed, choice.

"It would shift the balance of power in the consumers' favour and produce a more efficient market."