Marks & Spencer announced a bigger-than-expected rise in like-for-like sales of 5.3% in the second quarter of its financial year.
The retail chain beat City expectations in the 13 weeks to October 2, with general merchandise sales up 7% and food sales ahead 3.7%.
The retailer said its latest advertising campaign had driven customers to its stores and helped boost its clothing market share to 10.3%, but warned increased marketing would lead to operating costs at the top end of forecasts.
Chief executive Marc Bolland said: "Marks & Spencer has had a good second quarter, growing market share across all parts of the business."
He added that customers were "returning to quality" but warned that trading conditions are likely to become more challenging as disposable incomes come under greater pressure from increased VAT and spending cuts.
Mr Bolland added: "We are facing increased commodity prices and significantly tougher comparatives in the second half. As a result we remain cautious about the outlook for the remainder of this year and next."
The new chief executive joined M&S in May, having led a turnaround of supermarket Morrisons during his tenure there.
The Dutchman is expected to outline his strategy for the retailer in November when the company presents its half-year results.
The update follows largely positive trading reports from supermarkets Tesco and Sainsbury's earlier in the week.
Tesco posted a 12.5% rise in half-year profits to £1.6bn and UK like-for-like sales growth of 1.3% in the second quarter, while Sainsbury's saw sales growth of 2.9% in the same period.
M&S said a "record" autumn season on women's footwear helped boost clothing sales, while there was also strong demand for men's suits and knitwear.
The company said food's market share was up slightly to 3.7%, driven by 370 new products, including ready meal and biscuit ranges, as well as its Dine In and 3 for £10 offers.
The online shopping division M&S Direct saw sales shoot up by 49% in the quarter, and international sales were up 6.2%.
Freddie George, retail analyst at Seymour Price Research, said general merchandise sales had "real momentum" and food sales were benefiting from customers staying in at weekends to watch shows like X-Factor and Strictly Come Dancing.
He added: "We continue to believe that the strategy update, due to be given by Marc Bolland on the announcement of the interim results in November, will have a positive impact on the share price."