A new survey accuses Australian banks of aggressively encouraging customers to take on debt, regardless of their ability to pay it back, while pocketing $20bn in "super profits" due to unchecked market power.

The survey conducted by a think tank, the Australia Institute, found in the past 12 months, one in five respondents had had an offer to increase their available credit on their home loan.

Over the same period, two out of three respondents reported receiving an unsolicited offer for a new credit card, one in two had received an unsolicited offer to increase their credit-card limit, and one in three had received an offer for a personal loan, according to the survey.

The institute said "worryingly", a majority of respondents who were not in paid employment had received an unsolicited offer for a new credit card, while one in three people in low-income households had received an offer for a personal loan in the past year without seeking one out.

Australia Institute deputy director Josh Fear said the desire to maximise profit means the marketing of debt now drives the way banks behave. “What is not fully understood is that bank workers in Australia are often paid commissions to sell their bank’s products," Fear said. Consumers can no longer be confident that the advice they receive from bank workers is objective and suits their circumstances.”

The institute accused the big banks of reaping underlying profits of around $35bn per year, "$20 billion of which is ‘super profits’ earned because of their market power."

The institute's recommendations included legislation to ensure that interest rates charged by banks move in line with changes to the Reserve Bank cash rate, while being advertised as a mark-up over the official rate. Restrictions on sales targets and commissions for bank workers, banning pre-approvals of credit card offers or credit extensions, and a set of national laws to ensure the responsible provision of credit to consumers is also on the Australia Institute's agenda.

“Without this kind of policy intervention, the profits of the big banks will only get bigger at theexpense of the broader community,” Fear said.