Marks & Spencer's new Per Una clothing range has become a victim of its own success just a week after it was launched with demand so great that its roll-out programme has been delayed.

The British retail giant launched the long-awaited range, targeted at women aged between 25 and 35, in 30 of its leading stores on Friday.

Designed and supplied by George Davies, sales have been running at more than double targets which yesterday led to M&S and Mr Davies deciding to step back from a plan to open in 30 more stores today.

Instead, the group will launch Per Una in just 17 more stores. The plan to add another 30 a week later, to meet the original target of 90 stores, will be reviewed on Monday.

Mr Davies, said the decision had been taken to keep customers happy in the stores already open and that both he and M&S remained committed to selling Per Una in a total of 90 stores - but that it must be done when supply could be guaranteed.

"It was a difficult decision," he said. "But because we have already launched, we have to keep faith with the customers where we have opened.

"I think that what we have found is a bigger gap in the high street than I had ever thought - and it has been pent-up demand - people want great style, but also quality and affordability."

He added that he had no difficulties with supplying M&S with all the clothing it needed but that as sales were running so far ahead of projections, he needed more time to ratchet up the supply chain.