West Bromwich Building Society saw its assets burst through the #7 billion barrier to #7.2 billion as it posted record anual financial results for the ninth year running.
The society, the country's ninth largest mutual, has now grown sevenfold from just #1 billion of assets ten years ago, chief executive Andrew Messenger said.
Figures for the 12 months to March 31 showed the West Brom's mortgage book rose 21 per cent to #5.7 billion and its nets savings balances rose #400 million to #4 billion.
The society's pretax profit, excluding a gain of #3.8 million from the revaluation and sale of investment properties, jumped ten per cent to #34.7 million.
Mr Messenger, who recently announced his intention to retire at the end of September after ten years in the post, described the 2005/6 figures as "outstanding".
"This is our ninth consecutive year of record business results, and when you have been chief executive for ten years it doesn't come any better," he said.
West Brom members are benefiting from one of the lowest interest margins in the sector.
This measures the difference between the interest the society charges borrowers and the interest it pays to borrowers and last year the West Brom ratcheted it down further to 0.81 per cent for the core building society business.
Management costs were also down last year at 69p per #100 of assets compared with #1.93 a few years ago.
"We have long terms plans and goals centred around putting member value first," said 55-year-old Mr Messenger, who will be replaced by society operations director Stephen Karle, aged 46.
"This will involve growing our intermediary lending and our successful subsidiary businesses. Profits generated will be used to reward members for their contribution in a significant and increasing way, primarily through lower mortgage and higher savings rates."
With the building society sector undergoing some consolidation, mergers and acquisitions are on the agenda at the West Brom.
Mr Messenger yesterday confirmed to The Birmingham Post that the society had made a bid for the Kent Reliance, which is also believed to have been courted by the Yorkshire Building Society.
He would not disclose the value of the bid, but said it had been rejected.
The Kent Reliance is attractive to larger societies because of its offshore activities and its progress in turning itself into an exclusively internet-based business.
"We don't need to merge with anybody," he said. "But we will look at opportunities provided we think they offer long term benefits and provided we would be the dominant partner.
"The Kent Reliance approached us and we made an offer, but for one reason and another they decided to stay on their own. We hope we get a chance to talk to them again."
Mr Messenger went on to predict a stable housing market in the coming months, but said rising unemployment plus a likely increase in interest rates could cause problems, however. As a result, the West Brom "faces a year of greater uncertainty in the economy and the housing market than in recent years".