Marks & Spencer has suffered a further erosion of fashion market share, the latest Kantar fashion retail data has shown.

M&S’s clothing share by value slipped 0.7 percentage points in the 12 weeks to September 28 the figures, seen by Retail Week, indicate. The volume decline is understood to be greater.

The decline was greater than the 0.6 points over 24 weeks to the same date, likely reflecting the impact of September’s warm weather which hit fashion retailers across the board and prompted N Brown to warn on profits.

In the crucial womenswear category, M&S’s share was down 0.6 points in both periods.

September’s difficulties also appeared evident in Next’s showing in the period.

Its womenswear share was down 0.1 points over 12 weeks and flat over 24.

However, in fashion overall Next was up 0.3 points over the longer period and 0.2 points over 12.

Despite the fall at M&S, an observer pointed out that the retailer is focusing on full-price sales and believed margin is being preserved.

Earlier this month analysts at Morgan Stanley maintained in a note that course of action is right for M&S.

They said: “Top-line trends remain weak at M&S but margin recovery is not dependent on a sales recovery.”

The retailer will issue interim figures next week and, in the wake of the turmoil the weather has caused some fashion retailers, Morgan Stanley observed: “The fact that M&S has not felt it necessary to put out  a pre-close statement suggests to us that significant progress is being made on margins.”

The Kantar data also showed that Debenhams was flat in total fashion over 12 weeks and down 0.1 points over 24 – an improvement on the previous period.