A bank employee has blown the whistle on what she calls "morally disgusting" sales tactics being pushed by her bank.

She told RNZ about income protection insurance being sold to an elderly person, who because they were getting a pension, would never be able to claim it.

Then there is the emotional blackmail she said has been used on customers with children who are asked how they will feed their children if they are made redundant and do not have insurance.

The stories from the frontlines of the banking sector have come from a worker too afraid to identify themselves or the bank they work for, for fear they might be sacked for speaking out.

RNZ can reveal they work for one of the four big Australian-owned banks.

The worker said those who failed to meet sales targets for products like income protection insurance, life insurance and KiwiSaver funds were "performance managed."

The bank worker told RNZ the pressure on staff to sell more was intense and stressful and led to many taking sick days.

She talked about one elderly couple on a pension, who ended up paying $200 worth of premiums a fortnight to their bank for products, including income protection insurance.

She said many customers deferred to bank staff when they suggested they buy such products - and purchase them even if they did not need them - often returning to the bank later when they realised the expense.

RNZ found many people on the streets of Christchurch with stories about being given the hard sell by their bank, including Sha Shavz.

"I got a personal loan quite a while ago and they said [I should] get insured [with] life insurance, they were kind of predicting if I get cancer or some sickness that will cover it [my loan]. [They were] very insistent, very pushy."

Thomas Goldsmith's bank has also tried to upsell him.

"I went to apply for a credit card and she tried to sell me life insurance, home insurance, it just seems they get you while you're in there.

"So you're in there for something else and they try to sell you heaps of stuff, I think it's pretty annoying to be honest."

A budgeting mentor with the Care Waitakere Trust, Iain Davies, said income protection insurance was not something he would advise for most of his clients.

"We have clients who actually genuinely have to claim when they lose their job but their payments don't start for three months ... if you lose your job you don't want to wait, you need those payments to start now."

Mr Davies said he believed this sort of insurance was probably a better deal for the banks wanting to ensure continuing payments were made on mortgages, than it was for their customers.

RNZ approached the four main banks about the claims made by the unnamed bank worker.

ASB said it was interested in maintaining its customers' financial wellbeing and meeting its responsible lending obligations.

ANZ said only 25 per cent of its incentives for staff were based on sales and it did not have sales targets.

BNZ said it was committed to ensuring customers were not sold products they did not need or could not afford.

Westpac said the examples provided did not lead it to believe that the bank worker was a member of its staff.

The Financial Markets Authority is reviewing banking practices in light of problems found with the Australian banking sector, which is the subject of a royal commission of inquiry.