Marks & Spencer posted a 10 percent drop in first-half profit after second-quarter underlying sales fell for the first time in two years, underscoring the pressure on UK consumers.

The 127-year-old group, Britain's biggest clothing retailer which also sells homewares and upmarket food, said on Tuesday it made a profit before tax and one-off items of 315.2 million pounds in the 26 weeks to October 1.

That compares with analyst forecasts of 298-327 million pounds, with a consensus of 311 million pounds, according to a company poll, and 348.6 million pounds in the same period last year.

Sales from M&S' British stores open over a year fell 0.7 percent in the second quarter, with a 2.5 percent drop in general merchandise sales partially offset by a 1 percent rise in food.

Analysts had expected a 0.9 percent fall in total UK like-for-like sales, with a 2.8 percent decrease in general merchandise sales and a 1.1 percent rise in food.

Total first half sales, excluding VAT sales tax, increased 2.4 percent to 4.7 billion pounds, with market share maintained in clothing and food.

M&S said the second half had started in line with its expectations.

We remain cautious about the outlook but are well set up for the all important Christmas period, it said.

While retailers are hopeful of stronger demand this Christmas than last year, when sales were hit by heavy snowfall, analysts are worried high stock levels could lead to a frenzy of discounting that undermines profitability.

Britons have been reining in spending, with disposable incomes squeezed by rising prices, muted wages growth and government austerity measures, and as they fret about a stagnant housing market, job security and a fragile economic recovery.

Clothing chains have been suffering extra pressure from higher cotton prices and wage inflation in key manufacturing countries like China.

M&S, which is spending 600 million pounds over the next three years revamping stores, ended the half with net debt of 1.97 billion pounds and maintained its interim dividend at 6.2 pence.

Shares in M&S, which have lost 18 percent of their value over the last six months, closed Monday at 326 pence, valuing the business at 5.17 billion pounds.

(Reporting by James Davey, editing by Mark Potter)