The twin objectives of beauty and usefulness, which guided Susan Williams-Ellis throughout her career as a ceramics designer and manufacturer, were the self-same principles that governed her father, the architect Sir Clough Williams-Ellis when, from 1925 to 1975, he created Portmeirion village, the remarkable Italianate resort in Snowdonia. With Portmeirion village, Sir Clough said he wanted to show that “the development of a naturally beautiful site need not lead to its defilement”.

With Portmeirion Potteries, Susan Williams-Ellis declared, her aim was to make “good functional designs that were practical, beautiful and affordable”. She succeeded spectacularly, as nearly half a century's worth of satisfied customers would testify.

Susan Caroline Williams-Ellis was born in 1918 in the house of the critic and painter Roger Fry — an auspicious birthplace because Fry was the founder of the Omega Workshops, which famously encouraged the very thing to which Williams-Ellis would later devote her professional life: the aesthetic design and decoration of everyday functional objects.

Williams-Ellis's mother, Amabel Strachey, was a novelist, the daughter of an Editor of The Spectator and cousin of the Bloomsbury Group's Lytton Strachey. Fry was only one of the many distinguished friends from the world of the arts who visited the Williams-Ellis family homes in London and Wales.

Finding herself in the company of such luminaries as George Bernard Shaw, H.G. Wells and Bertrand Russell, the young Williams-Ellis saw at close quarters what could be accomplished by personal drive, focus and energy, and in later life she put into practice what she had observed. Not for nothing was she accustomed to being described as a human dynamo. If she could not sleep at night, she would drive in to her factory and talk to the night shift.

In her art-student days, too, she had impressive role models, studying ceramics with Bernard and David Leach at Dartington before moving on to study painting with Graham Sutherland and sculpture with Henry Moore at Chelsea School of Art. During the war, in which her younger brother Christopher was killed aged 21 at Cassino, she worked as a draughtswoman at the Air Ministry. In 1945 she married Euan Cooper-Willis, who had shared a room with Christopher at Cambridge. An economist and investment adviser, he became Williams-Ellis's right-hand man.

In 1948 they moved to a farm near Portmeirion, which they worked while she also did book illustrations and he was employed part-time with stockbrokers Grieveson, Grant in London. In 1953, with Williams-Ellis's father by this time in his seventies, they began taking over the management of Portmeiron village, including running the previously loss-making gift shop, which Williams-Ellis saw as an opportunity to start producing and selling her own ceramics.

At first she simply produced designs to decorate blanks — pottery shapes supplied by others — and these were applied to the pots by a small Stoke-on-Trent pottery-decorating company, A. E. Gray. In 1960 she and her husband bought Gray's workshop, and launched their own company there, which they named Portmeirion Potteries after its spiritual home in Wales. Then, in 1961, they bought a second Stoke-on-Trent company, Kirkham's. There, at last, she had the facilities to turn her own pottery, producing moulds from which the factory runs were made. Her working routine for much of the next 40 years was established.

Crucially for the firm's early success, she also made use of some cylindrical moulds, left behind at Kirkham's, from which medical and laboratory vessels had been produced. She took these moulds, carved bold, primitive patterns into them, and launched in 1963 a sensationally different, topically psychedelic range which she named Totem — tall, straight-sided coffee and tea sets in blue, amber or dark green with a translucent flow glaze. Later she added new pieces and introduced new colours, including a dramatic use of white.

With its simple, clean lines and abstract, embossed patterns, Totem was ideal for the dining rooms of the Sixties and Seventies and in no time received the dubious compliment of rival firms cashing in on its success by making copies. The genuine pieces are now collector's items, with the rarer ones fetching several hundred pounds at auction, with museums as well as individuals only too delighted to add them to their collections.

Within only a few years of her pottery being launched, Totem had firmly established Williams-Ellis as a trendsetting ceramicist, but she had no intention of resting on her laurels, and constantly experimented with new glazes, colours and shapes. A particular stroke of genius was her Botanic Garden range of florally decorated tableware introduced in 1972. Until that time the convention had been that tableware sets should match exactly, and it was against the advice of department-store buyers that Williams-Ellis bravely launched this mix-and-match set with its 28 different plant motifs (albeit within the same leaf border). Phenomenal sales soon proved that the canny potter had rightly discerned a new mood of informality in the nation's dining habits.

The range became a worldwide bestseller, accounting for about 50 per cent of the company's turnover, and continually developing as new motifs, new colour emphases and new products were added to reflect changing tastes. Botanic Garden helped Portmeirion Potteries weather 20th-century recessions, win the Queen's Award for Export Achievement (in 1989) and sell in more than 34 countries around the world. But its success never persuaded Williams-Ellis of the virtues of standing still. In 2002, for instance, aged 84, she was still playing a dynamic role in acquiring for Portmeirion Potteries the eye-catching photographic-manipulation skills of the tableware and accessories designer Ella Doran, whose range was seen by some as the contemporary equivalent of what Williams-Ellis herself had done with Botanic Garden 30 years before.

Another interest was the under- water world of coral reefs, which, with the help of a snorkel and fins, Williams-Ellis sketched on waterproof board and plastic paper. In 2002 she staged an exhibition of her marine-life paintings, which of course, as a professional ceramicist, she could not resist transferring onto limited-edition ceramic plates.

In 2003 Keele University awarded her an honorary master's degree for her outstanding contribution to the ceramics industry, and in 2005 — the year she retired from an active role with Portmeirion Potteries — the University of the Arts, London, made her an honorary fellow.

She is survived by her husband (a former chairman of Portmeirion Potteries), and by their four children, three of whom work for Portmeirion Potteries or Portmeirion village.

Susan Williams-Ellis, ceramics designer, was born on June 6, 1918. She died on November 27, 2007, aged 89