Both banks also stood out for their upselling practices.
The survey found these customers were more likely to report being offered financial products including credit cards without requesting them.
Overall, 27 per cent of customers reported receiving unsolicited offers from their bank for products ranging from insurance to mortgage top-ups.
The most common offers were credit cards and increases in credit card limits.
"While there's nothing wrong with banks letting their customers know about new products, the practice raises questions for us about the banks' compliance with their responsible lending obligations," Chetwin said.
By law, lenders must ensure credit is suitable for borrowers and meets their needs.
"Our survey found less than half of the customers who got these offers thought the product was a good option," she said.
Of those offered a new credit card or an increase in their card limit, only about one in three thought it suited their needs.
Customer satisfaction scores
• TSB: 87 per cent
• The Co-operative Bank: 82 per cent
• Kiwibank: 71 per cent
• BNZ: 65 per cent
• Westpac: 55 per cent
• ANZ: 52 per cent
• ASB: 52 per cent