KiwiBank has rejected criticism that it is failing to meet its social responsibility obligations by closing branches in poorer suburbs.
Labour Party MP Brendon Burns has raised concerns with KiwiBank's parent company, New Zealand Post, at Parliament's Commerce Select Committee.
Mr Burns is particularly concerned that the branch in the Christchurch suburb of Linwood is being closed.
He says Linwood is a poor suburb and the closure goes against KiwiBank's social obligations and its stated intention of serving low income clients.
But NZ Post chairman Jim Bolger says KiwiBank's ambition had never been solely to provide services for low income people.
He says KiwiBank is continuing to grow and its success has helped offset difficulties in other parts of NZ Post's business.
Mr Bolger says the postal service delivered 65 million fewer letters in last financial year, than the year before, a drop of 7%.