"We're just easy picking," she said.
Although banks aren't legally allowed to discriminate against workers due to occupation, they do have the discretionary power to decline credit or products to certain industries.
Brennan said her business has worked with BNZ for many years and hasn't had any problems with the bank.
A BNZ spokesperson says that while the bank doesn't decline banking services to individual customers based on their occupations, it can decline credit or banking products to businesses in certain circumstances.
The spokesperson said this includes payday and fringe lenders; businesses engaged in prostitution and brothel keeping; tobacco manufacturers and producers; businesses involved in illegal activities or unethical labour practices; weapons manufacturers subject to international prohibitions; and nuclear-related companies.
A representative from the Bankers' Association told the Herald there is no industry standard on these issues and that each bank decides on its policies independently within the remit of the law.
According to Brennan, banks aren't the only organisations making life difficult for sex workers.
For instance, she often recommends to the women working within her business to list a different – more acceptable – occupation when filling in ACC forms to avoid being treated with prejudice.
"If they're honest about being a sex worker, they're treated as if they're about to commit a crime," Brennan said.