The transformation of Marks & Spencer’s away from its increasingly staid and frumpy image has been credited to that bastion of staid frumpiness – the Women’s Institute.

The doughty women of the WI have been at the heart of a three-year campaign to revamp the store’s fashion collections, which has led to a remarkable recovery in high street profits, The Times can disclose.

M&S even credits the women for doubling the order of a fluted printed skirt on sale in selected stores last year. It was so popular that in January it was restocked and sent to all 520 stores in the country.

Faced three years ago with plummeting sales and accusations that they had stopped listening to their customers, Stuart Rose, the new chief executive, made the crucial decision to forge a bond not with the teenagers streaming past M&S’s doors on their way to Topshop or to the Yummy Mummies leafing through Boden catalogues – but to the Jam and Jerusalem brigade.

A total of 800 WI members in Kent, Buckinghamshire and Leicestershire formed a unique focus group that has helped the company to choose its innovative new collections.

They gave the thumbs up to a number of items which became fashion hits, including last season’s checked waterfall-fronted jacket that was modelled by Twiggy in television and print advertisements.

The women have been given a special duty to vet the classic collection and a £25 cotton three-quarter length sleeved candy-striped shirt in pink, blue, lilac and white, which is this summer’s bestseller.

When the WI women were given first vetting of a pink Tencel linen shirt-waisted dress they complained that the sleeves were too short. The dress, now with longer sleeves, goes on sale next week at £49.50.

When Mr Rose was appointed three years ago he told his senior managers that the store had stopped listening to its customers and he wanted them to find out what shoppers liked and what they wanted to buy.

Kate Bostock, head of womenswear who has also been given responsibility for lingerie, knew immediately where to turn for help. Her mother was a WI stalwart.

Approaches were made to various branches and the WI formed the first new M&S focus group for the Rose management regime.

M&S disclosed the link after being asked why Mr Rose had agreed to speak at today’s WI annual general meeting at the Royal Albert Hall in Kensing-ton, Southwest London. Surely the WI was not the company’s target audience?

A company spokeswoman gave the surprising reply: “We believe the WI membership represents our core customer base. We have worked together on various issues for many years and have shared values.”

The firm is conscious that the views of the 800 regular WI vetters are probably shared by many of the 200,000-plus members around the country, who in turn represent women buyers.

The spokeswoman said: “A special focus group was created for the classic collection which involved over 800 members of the WI. They gave a thumbs up to the improved quality and fit of fabrics but said they wanted to see more fashionable items in the collection.

“Their feedback has had a direct impact on our buying. They are really keen on being fashionable and that has helped us design new collections.”

Fay Mansell, chair of the National Federation of WIs, was pleased that members had made such an impression in the high street. She said that links with Marks & Spencer were arranged by individual branches, not by headquarters.

She also did not think that all members were M&S shoppers but added: “WI members are a bedrock of sound and common sense. They get their opinions heard and and acted upon.”

Mr Rose announced last week that pretax profits had leapt 29 per cent to £965.2 million and sales were up 10.1 per cent to £8.6 billion. Some members of the WI at the AGM today may be expecting a pat on the back for their part in the turnaround.

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