Net mortgage lending at Coventry was £1.2bn at the start of this year - accounting for 25 per cent of mortgage growth in the UK since the start of 2010.
Gross mortgage advances totalled £2.9bn, a record for the society in terms of both value and market share.
Profit before tax at the society increased by 18 per cent to £62.2m for the first six months of 2013, up from £52.8m for the start of 2012.
The society also boasted that in the most recent table published by the Financial Ombudsman Service, Coventry had the lowest proportion of complaints upheld of any high street bank or building society listed.
No individual member of staff is incentivised to sell products and hasn’t been since 2010.
David Stewart, chief executive of Coventry, said: “Coventry has maintained its track record of strong performance which was established before the onset of the current financial crisis in late 2007.
“We remain the most cost-efficient building society in the UK, the quality of our lending is exemplary, and our core tier one capital ratios show us to be amongst the strongest of UK financial institutions.
“Although these achievements may not be guaranteed by a mutual business model, Coventry continues to demonstrate that building societies can thrive in the toughest of environments.”