Yet more bad data for the Big Four was released today - plus a hint that there could be a fresh problem facing the UK's supermarket sector, in the form of Amazon Fresh.
Sainsbury was the only supermarket among the Big Four to keep pace with the sector's growth over the last quarter, with Asda's market share continuing to tumble as Morrisons and Tesco also look bruised. Sales at Sainsbury were up 0.9 per cent, in line with the sector as a whole, while spend at Asda fell 2.9 per cent, according to Kantar Worldpanel.
Revenues at Tesco's Express convenience stores actually grew, but were not enough to stave off declines through the rest of its store portfolio, meaning total sales were down one per cent in the 12 weeks to 13 September. Sales at Morrisons continued their downwards trajectory, falling 1.4 per cent.
The sector is still struggling to shake off its woes: this is the six month in a row that sales at the UK's grocers have increased by less than one per cent.
But there are some success stories among the usual suspects. Aldi and Lidl have maintained their double-digit growth - up 17.3 per cent and 16 per cent respectively. In the past 12 weeks 56 per cent of British households have visited one of the two discount grocers.
Waitrose is also growing above the sector average, with sales up 2.9 per cent, while sales at the Co-operative were up one per cent. Iceland grew 3.4 per cent during the same period.
However Kantar warned there could be yet another challenge facing the sector in the form of Amazon's new online food delivery service Amazon Fresh.
Fraser McKevitt, head of retail and consumer insight at Kantar Worldpanel, said: Fraser McKevitt continues: “With shoppers moving their custom away from the traditional, larger-size supermarket stores, online sales are continuing to boom and are up by 12 per cent compared with a year ago.
"Almost seven per cent of grocery sales are currently purchased through the internet and existing online supermarkets will be watching closely to see when Amazon Fresh will launch in the UK and whether it will steal market share or grow the online market even further.”
Neil Saunders, managing director of analyst firm Columino, told City AM that Amazon Fresh would be a "very unwelcome additional pressure into a market that is already oversupplied". But he said Amazon's success in cracking the UK's grocery sector should not be seen as certain.
"People get very excited about Amazon and think it's very savvy, which is true in non-food, but food is a much more challenging market. So far it hasn't been that successful in the US and the UK is a much more intense, more competitive market online, with very well-known big brands.
"We shouldn't look at Amazon as this automatic success story - it will come to the UK as an underdog and have to work very hard to make it work economically. It's definitely unhelpful [to the Big Four] but I don't think it will conquer all overnight."