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Britain's Nationwide reports first half profits fall 33%

LONDON, Nov 22 (Reuters) - Britain's Nationwide Building Society reported a 33% fall in profit for the first half of its financial year, as it took a fresh charge for mis-selling insurance products and saw its interest margin fall.

The bellwether mortgage lender said its underlying profit fell to 307 million pounds ($396.67 million) in the April-September period from 460 million pounds a year ago.

Nationwide's net interest margin - a closely-watched measure of underlying profitability - fell to 1.12%, down from 1.23% a year ago as competition in the mortgage market continues to bite. ($1 = 0.7739 pounds) (Reporting By Lawrence White Editing by Rachel Armstrong)