Doubts the Reserve Bank's tightening of lending ratios will constrain ballooning house prices

The Government's given the bank the green-light to reduce the number of buyers borrowing huge sums of money for mortgages.

It clears the way for the Reserve Bank to develop a new debt-to-income restriction, so long as it avoids hitting first home buyers.

New rules restricting risky lending could be in place from October.

Infometrics principal economist Brad Olsen says this change won't making housing cheaper or more accessible any time soon.

He says it is instead designed to ensure the lending system remains viable long-term.