The booming housing market has failed to avert a mortgage lending slump at Britain's biggest building society.

Nationwide, which employs about 2,000 people at its Swindon headquarters, saw its residential net mortgage market share down to 0.2 per cent for the six months to October 4, a major decrease on last year's figure of 10.1 per cent.

Gross approvals fell from £6 billion to £4.7 billion, while net advances were £100 million compared with £3.2 billion a year ago.

A spokesman said increased competition was partly responsible for the decline; lenders have rushed to snap up customers as interest rates hit record lows.

But the main reason for the fall was because Nationwide has repriced its mortgages, slashing the number of bargain deals on offer.

The spokesman said the decline was expected: "A lot of our competitors are still offering loss-leading products that are uneconomical and we absolutely refuse to price our mortgages unfairly. It is not fair and it is not sustainable.

"We are a building society run for our members' benefit so market share is not the only way to measure success."

Nationwide's overall mortgage market share which takes into account not just the amount of business won and lost but also the lender's size, assets and other factors was unchanged at 8.5 per cent.

As well as mortgages, Nationwide offers loans, savings products and current accounts.

Total income across the group for the six months to October 4 rose from £612.6 million to £627.5 million.

Pre-tax profits, however, slipped from £253.8 million last year to £206.8 million.

Philip Williamson, who takes over as chief executive from Brian Davis at the end of the year, said: "Our strategy of putting our members first has meant we have delivered a record £210 million in member benefits in the first six months.

"We are proud of the benefits we've delivered to our members and intend to build on this very strong performance in the second half of the year.

"With no shareholders to pay dividends to Nationwide can offer better rates and fewer charges than the banks. Our mortgage pricing strategy is based on fairness. The strategy is working well."