More than six in 10 shoppers visited either Aldi or Lidl in the past three months, according to the latest Kantar Worldpanel data.
Symbols and independents, Iceland, the discounters, the big four supermarkets and Waitrose all increased sales in the 12 weeks to September 10.
Lidl led the pack, showing 19.2% growth to achieve sales of £1.35bn, followed by Aldi, up 15.6% to £1.78bn.
Fraser McKevitt, head of retail and consumer insight at Kantar Worldpanel, said: “Collectively Aldi and Lidl now account for nearly £1 in every £8 spent in Britain’s supermarkets – a decade ago this was only £1 in £25.
“In the past three months almost 63% of shoppers visited one of the two retailers, up from a level of 58.5% last year.”
Some 98% of households still shopped in at least one of the big four over the same three-month period despite the growth of the discounters.
McKevitt said Tesco’s recovery was becoming more entrenched.
“Sales have grown continually since April this year and are up by 2.7% in the past 12 weeks, though the retailer’s market share remains under pressure, squeezed by 0.3 percentage points to 27.8%.
“At Morrisons, volume sales have risen for the first time since January and sales of its premium ‘The Best’ line are up 38% year-on-year, making it the fastest growing premium range in a market where top-tier products are outperforming all other lines.”
In contrast, sales at co-operatives have fallen for the second consecutive month to knock 0.3 percentage points off their grocery market share to 6.3%, Co-op sales, which includes all retail societies that sell food, fell 1.6% to £1.61bn
The sales dip was in sharp contrast to the comparable period last year when they climbed 6.6% to £1.63bn.
Sainsbury’s market share fell 0.2 percentage points to 15.7% despite an average sales increase across its convenience, supermarket and online channels of 2.1%.
Iceland’s sales increased for an 18th consecutive period, up 5% year on year although its market share has remained flat at 2.1%
Symbols’ and Independents’ market share held steady at 1.9% - with sales up 1% to £486m.