Marks & Spencer saw like-for-like sales sink back 5.3% for the 13 weeks ended June 28.
M&S' general merchandise like-for-like sales, which includes clothing, were down 6.2% for the period.
M&S group sales rose 1.3% for the period, but UK total sales fell by 0.5%. Total general merchandise sales was down 2.7% and within that clothing sales fell back 3.6%.
International sales were up 24.5%.
M&S chairman Sir Stuart Rose said: "At our preliminary results in May, we reported a mixed start to our 2008/9 financial year and expressed caution about consumer sentiment. Since then, consumer confidence levels have deteriorated markedly and market conditions have become more challenging."
Rose added: "General merchandise has been affected by the current market conditions, but we are holding market share in clothing, and home continues to outperform. Stock levels have been well controlled and our Summer sale will start at the same time as last year."
"We expect market conditions to remain difficult and we are managing our business accordingly. As we said in May, tight stock control and management of costs are a priority. We continue to expect gains in bought-in margin, although the outturn on gross margin is difficult to predict and will depend on market conditions and our trading stance. Our guidance on operating costs remains unchanged."
"Four years ago, M&S was a weak business in a strong market. Today, we are a strong business in a weak market. Our work to reposition the business in terms of product and values, service and store environment, coupled with our strong balance sheet and cash flows, places us well for the short term while enabling us to continue to invest for the future."
Food sales also fell back 4.5% like for like and Steven Esom, director of food, has stepped down from the board effective immediately. John Dixon, currently director of home and M&S Direct, will replace Esom.