Supermarket chain Sainsbury‘s‘ CEO Justin King has attacked plans outlined by the Government to permanently extend Sunday trading hours, saying that the existing rules had “great merit” for both customers and staff.

In an open letter to The Sunday Telegraph, King waded into the argument around Sunday trading laws, following a proposed extension which would see stores able to open for 24 hours on Sundays, an initiative initially introduced to cope with increased demand over the course of the Olympic Games.

Last week, a Sainsbury‘s spokesperson rejected the possibility of an extension, commenting: “We don‘t believe people are looking for Sunday trading to be extended on a permanent basis, with both customers and colleagues seeing the current status quo as a good British compromise.”

King believes that the restrictions on opening hours should be maintained, despite claims from Tory MP‘s that changing the law may boost the retail sector during this difficult trading period.

King wrote: “Maintaining Sunday‘s special status has great merit for our customers and our colleagues, and relaxing Sunday trading laws is certainly not a magic answer to economic regeneration.”

Shop workers‘ union Usdaw, which last week wrote to Business Secretary Vince Cable highlighting the “very detrimental impact” of such a change on its members, also wrote to the paper in conjunction with the Association of Convenience Stores CEO James Lowman and the Bishop of Oxford.

The joint letter read: “With margins being squeezed and sales flatlining, the last thing the retail sector needs is increased overheads for little or no return. Longer opening hours won‘t put more money in the pockets of shoppers.”