Amazon has quadrupled the number of grocery products it sells under its Subscribe & Save model since October.

More than 8,500 grocery products can now be bought through Subscribe & Save, which allows consumers to sign up for regular bulk deliveries of staple household and larder products in exchange for discounts of at least 10%.

The products available under the model are all shipped directly by Amazon so shoppers can buy more than one product without racking up delivery charges from different distributors.

Twenty per cent of groceries sold on Amazon are distributed directly - up from 15% in October.

Amazon is continuing to invest in its UK grocery business despite struggling to contain costs. Last week, it reported a 45% drop in operating profit in the fourth quarter despite increasing sales by 35% to £17.43bn.

“Analysts will be questioning how long Amazon can continue to invest ahead of the curve without reaping the benefits,” said Siobhan Gehin, an associate partner of the management consultancy Kurt Salmon.