Sainsbury’s online non-food growth is being constrained by its store sizes, chief executive Justin King has said.

In particular, he conceded that the grocer has yet to launch an online clothing offer because the amount of space it can allocate to non-food in stores and its in-store picking model do not allow this. “Online is still mainly about food,” he said.

He added: “Ourselves and Tesco are still about picking in-store and we don’t have a sufficiently large offer in-store to support this.”

He said that the key to incorporating non-food and raising online sales was to “get the food right first and then the store size – it’s a sequential thing”.

The UK’s third-largest grocer introduced shoppers to its biggest non-food offer to date at London Colney in Hertfordshire last week, where 25,000 sq ft of the store’s 85,000 sq ft is devoted to non-food. The shop features its first digital hub, with TV, audio and digital photography brought together in one area.

Separately, King ruled out banning plastic carrier bags from the chain’s stores, unless there is legislation.

He warned that switching to paper bags would be counter-productive, because their weight and the energy required to get them to stores mean that they have greater environmental impact than plastic bags.

Asked whether he approved of the London boroughs’ bill to banish plastic bags from the capital’s shops, he said: “We will oppose this until there is legislation to make us do it.”

A week after Delta Two’s£10.6 billion bid collapsed, Sainsbury’s unveiled a joint venture with property giant Land Securities to unlock£113 million worth of freehold assets.

Sainsbury’s delivered underlying pre-tax profits of£232 million this week for the six months to October 6, compared with£194 million for the same period last year.

This was achieved on the back of a 4.7 per cent uplift in total sales to£9.9 billion, giving a 4 per cent like-for-like sales rise, excluding petrol.