The group, which operates brands such as Kent Reliance and Interbay Commercial, said its total mortgage origination had grown 121% to £794m.
It also purchased £182m worth of mortgages for £133m from other sources during the year.
Speculation the bank is preparing to float, first reported by Mortgage Solutions in December, has continued but OneSavings Bank did not set out any plans within its yearly report.
Of its mortgage lending £227m was on residential property and the lender said it had started the new year with a ‘very strong’ pipeline.
Andy Golding, chief executive of OneSavings Bank, said: “In 2013 we attracted more savers and borrowers whilst keeping costs well controlled and continuing to grow our net interest income.
“The profitability in 2013 enables us not only to continue to grow in the future as it increases our capital base, but also to ensure that our offering to customers really does provide value for money.
“Trading so far this year has surpassed management expectations. The strong upwards trend in applications and new mortgage completions we witnessed last year has been maintained. At the same time, funding costs have continued to fall, further expanding our net interest margin. We are confident that the Group can make further progress in 2014.”
