By Harriet Morris and Catherine Bosley

LONDON (Reuters) - London fashion designers say mass retailers do not necessarily undermine their business and can actually be of help, but acknowledge that they have awakened a desire among shoppers for frequent refreshing of stock.

In the past, luxury labels came up with designs that months later retailers interpreted for the general public.

But with photos available online within minutes of a fashion show ending, stores such as H&M and Topshop, have cut the time span between catwalk and store.

"It's not competitive, it's complementary," said David Cohen, managing director for the label Betty Jackson, which produces a line for department store Debenhams.

"If we were only a (high fashion) label we would be dying because we have not got the backers, we have not got the big support financially," he said, though he acknowledged that he was sometimes frustrated by chains whom he suspected of pilfering Jackson's ideas.

Traditionally, designers created two collections a year and shipped new wares for spring and fall. But mass retailers broke with this practice, attracting shoppers by varying their stock, analysts said.

This in turn put pressure on designers to come up with more collections to satisfy orders from department stores, they said.

NEED FOR NEWNESS

Richard Hyman of the consultancy Deloitte said that stores catering to people with smaller budgets were the fastest-growing segment of British retail in the past decade and that the amount of clothing an average woman bought rose nearly ten fold.

"The need for newness is increasing. Not so many years ago, it was the luxury end that was influencing. The point of view of the designers percolated down progressively," Hyman said.

"Not only have (high street stores) closed the gap, but they've set a new pace of their own."

At Nicole Farhi, Managing Director Niki Scordi said mass retail posed a challenge.

"You do have to keep refreshing. It's forcing designers to deliver earlier and earlier, she said, explaining that deliveries of spring/summer 2010 stock would begin in November. "But it keeps it fresh as well for the customer." Up-and-coming Italian-born designer Maria Francesca Pepe, whose clothes are sold by Henri Bendel in New York, agreed. "I don't think they clash," she told Reuters.

"I am part of the beginning world, where the ideas grow, where the new inspiration and new techniques (come from)," she said, pointing out that high street stores relied on others to generate ideas. "It doesn't affect the person who comes to buy my product."

(Editing by XXX))