Mothers now have an average of three supermarkets at which they do their main shop, and almost a quarter visit more than one during a single expedition, a survey has found.

The poll found that "loyalty is a thing of the past", with a third (33%) of mothers claiming to have switched supermarkets in the last six months, according to the report by Starcom MediaVest Group with parenting website Mumsnet.

Some 10% claim to have switched from the "big four" - Tesco, Asda, Sainsbury's and Morrisons - in favour of discount retailers such as Aldi and Lidl.

There has also been a "dramatic "shift in the ritual of the weekly food shop ritual, with more than half of mothers topping up at least twice throughout the week.

A third of Marks & Spencer and Waitrose shoppers top up at least three times a week, the survey found, compared to just under a quarter of Aldi shoppers.

The poll showed the discounters were not just frequented by those with below-average household incomes, with 24% of respondents who earn between £50,000 and £69,000 and 21% who earn £70,000 and £99,000 describing themselves as Aldi shoppers.

Almost a quarter (22%) of respondents within the £70,000 to £99,000 salary bracket said they shopped at Lidl.

Starcom MediaVest Group co-chief executive Steve Parker said: "Consumers' shopping habits are changing and we now have more control on where and how we shop than ever before.

"Supermarkets can no longer depend upon loyalty. Instead, each must make sure it is central to mums' shopping repertoire.

Mumsnet chief executive Justine Roberts said: "Mums are still the most important consumers to supermarkets, as they are the ones who usually perform the weekly shop.

"But within this group shopper behaviour is rapidly changing, meaning it's vital for supermarkets and retailers to understand what mothers are looking for the when they decide where to shop and communicate with them at relevant times in relevant ways to ensure they regularly return."

:: Starcom MediaVest surveyed 1,000 Mumsnet members online in September.