A whole new attitude is required from retailers if they are to compete with the likes of Amazon

As brands expanded across the country, it was a tool that allowed stakeholders to understand how a retailer was actually performing.

The measure has gradually become the benchmark for assessing the success or failure of a retailer. It has become even more influential since the recession and online shopping revolution sparked the collapse of famous names such as Woolworths.

Yet the validity of like-for-likes has long been debated. The old saying in retail is that ‘sales are vanity and profits are sanity’, so critics of like-for-likes have argued that encouraging businesses to focus on sales per square foot is dangerous.

But also, the measure itself has never been properly standardised. Somewhat ironically, comparing the performance of one shop year-on-year is not like-for-like to all retailers. Some include extensions to the shop, others include purchases using vouchers and gift cards. Some retailers do not even report like-for-like sales, such as Next and Sports Direct. One look at the share prices of these companies will show you that it has done them little harm.

With bricks and mortar retailing and online shopping moving ever closer, and other new formats such as discounting and convenience growing rapidly, like-for-like sales now look more outdated than ever. For a true judge of how a retailer is performing, it is time to go back to the old-fashioned measures of total sales and pre-tax profits.

Take supermarkets. In the last quarter, Tesco reported a 1.3% fall in like-for-like sales and Sainsbury’s suffered a 2.1% drop. But you cannot conclude from this statistic that Tesco is outperforming its rival. These two retailers are currently operating in different dimensions. City analysts believe that Tesco is actually losing money in the UK at present, while Sainsbury’s is forecast to make a pre-tax profit of £675m in the next year. Tesco is throwing all the money it has at cutting prices and improving customer service in an attempt to win back shoppers, while Sainsbury’s is attempting to hold firm against the chaos in the industry.

To be fair to the retailers, their like-for-like declines also do not reflect the fact that prices are falling due to the industry price war and falling commodity prices. Sales volumes - the amount of products a supermarket sells - are actually rising for the first time in years.

Like-for-like sales take no account of the costs of adapting a business for the modern world, but they also take little account of the benefits.

With online and physical shopping converging into what John Lewis calls the “omnichannel world”, what do like-for-like sales actually mean? If a shopper browses products in a John Lewis shop then buys the product online, should that sale be allocated to the store or online? And if a shopper buys a product online then collects it in store, who is that allocated to?

In M&S’s last trading update, the company said that online sales rose 39%, despite a fall in like-for-like sales in its general merchandise arm, which is primarily clothing.

Both the like-for-like sales and online sales measures should disappear. Sensible retailers are already allocating online sales to the nearest store. This recognises that the local store will bear much of the cost if the online order is fulfilled from the stock of the shop, but this also motivates the staff in the store to try to boost online sales.

If physical retailers are to fight back against the likes of Amazon and Asos, this is the attitude that is required. Total sales and profits are what matter.

Like-for-like sales emerged due to industry circumstances in the 1980s, notably the property boom. They prevented retailers using expansion to pull the wool over the eyes of stakeholders about the real performance of a shop. Now, with new circumstances for the industry in the 21st century, like-for-like sales should disappear.

Graham Ruddick is deputy business editor (retail and technology) at The Telegraph