Cost reductions and surging loan volumes have propelled Bank Australia to a record net profit of A$13.3 million for the six months to the end of December.The bank announced the unaudited first half result on Wednesday, highlighting that it was continuing to grow market share in retail deposits and lending.Bank Australia grew its loan base by 5.1 per cent during the half year, while deposits grew by just under 10 per cent.The bottom line result is $2.9 million up on the corresponding period in 2016 and constitutes a 28 per cent rise in interim earnings."While growth has moderated from the levels seen over the past two financial years, the bank continues to grow sustainably at a rate above the wider banking sector," said managing director, Damien Walsh."In a continuing low interest rate environment, we have kept our prices competitive while generating profit to invest in the bank."Bank Australia has a unique business model in the local market that is based on linking its banking services to environmental and social responsibility.The strategy has cultivated a unique customer base, which now distinguishes the institution from its peers in the mutual banking movement.The bank's differentiation is reflected in the composition of its rapidly growing liability book, which includes more than $1 billion from non-retail customers.Government customers have been the fastest-growing source of new deposits in the last three years, having grown their contributions to the bank's vaults from around $100 million in 2014 to $220 million at the end of December.This makes Bank Australia the second-largest mutual deposit-taker in the Australian government sector behind IMB Ltd.According to APRA's latest monthly statistics, the bank also holds $800 million on behalf of community organisations and business customers.Walsh believes the bank can continue to grow market share this year by leveraging its responsible banking credentials."We have focused on improving our customers' experience when engaging with the bank, responded to customer and societal needs and continued our work to create a healthier planet," he said."We are confident that our responsible approach to banking and the continued success of our 'the bank Australia needs' campaign will lead to continued profitable growth in the second half."