The retailer said like-for-like general merchandise sales dropped 1.3% between July and September on a year earlier, slightly above City hopes and better than a 1.6% first-quarter decline.
Underlying pre-tax profits dropped 8.9% to £261.6 million during the six months to the end of September, weighed down by the cost of the star-studded launch of its autumn/winter clothing range.
Chief executive Marc Bolland said its revamp of womenswear was its key priority during the period, and is showing "early signs of improvement".
But the high street bellwether said that, while consumer confidence appears to be improving, there is little evidence of this translating into higher spending, adding that it is cautious on the outlook for the rest of the year.
Like-for-like sales in its food business rose 3.2% in its second quarter.
Under pressure to stem sliding clothing sales, M&S launched its Leading Ladies campaign, featuring a dozen high-profile women including actress Dame Helen Mirren and Olympic boxer Nicola Adams, in September.
M&S said the new clothing range was only in its stores for three weeks of the period, adding that it has also rolled out a more "inspiring" store layout. The company said it is targeting a "steady improvement in performance as our customers begin to notice the changes".
The retailer said it is "well set up" for its key Christmas period, with more innovation and choice, and its overall expectations for the rest of the year are unchanged.
But it added: "Given continued pressure on disposable incomes, we remain cautious about the outlook for the remainder of the year."
The retailer hailed a "strong" performance in food, international and its online business. It opened 26 international stores during the half, and expects to open more than 50 during the rest of its financial year.
As well as the clothing launch, its profit margin in the UK was also hurt by a "more aggressive end of season clearance" and the earlier timing of its mid-season sale, which depressed earnings in its general merchandise division.
But margins in its food business increased with better buying and management of promotions helping offset higher ingredient prices.
The group's underlying UK sales increased 1.1% during the second quarter, an improvement on a 0.3% gain in its first quarter, to give a 0.7% first half increase in like-for-like sales.
Total sales increased 3.9% to £4.88 billion.