OSB saw originations of £627m and upped new lending from £204m in Q1 2015 to £329m.
The Bank said that "despite the introduction of the bank tax surcharge, return on equity was strong in the first quarter and we are on track to deliver a return comfortably ahead of our financial target".
Andy Golding, CEO of OneSavings Bank, said:
"I am extremely pleased with the performance of the business so far this year. We achieved strong levels of new business in the first quarter with £627m of organic origination at attractive margins, supported by acquisitions of £131m.
As expected, March was a record month as we fulfilled heightened demand to accelerate mortgage completions ahead of stamp duty changes. Intermediary focus has now returned to new applications and we are confident in achieving our full year growth targets."
