Mortgage rates for US homeowners have spiked to levels not seen since before Fannie Mae and Freddie Mac were taken into government supervision, a side effect of the US Treasury's latest attempts to rescue the financial system by shoring up bank balance sheets.

Interest rates on 30-year fixed-rate mortgages were at 6.38 per cent yesterday, against 5.87 per cent before the Treasury's latest actions, according to Bankrate.com.