Bollard cut the official cash rate (OCR) from 3% to 2.5% on March 10.

Kiwibank passed on Bollard's cut to new customers taking on floating-rate mortgages immediately but its existing customers with floating rate mortgages have to wait until March 28.

The four major Australian-owned banks took between one and four days to pass on the cut for new customers but their existing customers have to wait until March 24, in the case of BNZ, and up to April 4, in the case of ASB Bank.

One site reader, who describes herself as a disgruntled ANZ Bank customer, questions whether the banks are taking the opportunity to profiteer at their customers' expense.

ANZ passed on the cut to new customers on March 12 but won't pass on the cut to existing customers until March 28. Interestingly, the ANZ-owned National Bank didn't pass it on to new customers until March 14 and its existing customers have to wait until March 29.

"The National Bank and ANZ operate on two different systems with differing system constraints around rate-change timings," says ANZ National spokeswoman Lyn Holland.

Another reader says he emailed his bank manager as to why his bank, Westpac, wasn't passing on the cut until March 31. "He never replied - probably too embarrassed. Now he has his out-of-office on."

Yet another says: "Banks should drop floating rates immediately the change is announced. The floating rate should be just that - floating."

One reader says: "I reckon its just a money grab. They know that no one will bother refinancing if they are getting the lower rate in about a month's time."

All the banks say it's a matter of the constraints of their systems and the requirement to give their customers notice. Customers experience exactly the same delays where the OCR rises, they says.

BNZ spokeswoman Emily Davies' response is typical: "The CCCFA (Credit Contracts and Consumer Finance Act 2003) regulations require existing customers to be notified of any changes to their repayments within five working days of the change.

"While we can put new customers on the changed rate straight away, we need to allow a reasonable timeframe to inform existing customers. Our process is identical for any mortgage rate change," Davies says.

Which is unlikely to satisfy the complainers: "Unfortunately, it's all connected with legal issues and the banks like too hide behind them," says one site reader.