AMP has revealed that it expects writedowns of up to A$1.2 bn (£428m) at its UK and European businesses.
The announcement means AMP is likely to post a substantial loss for 2002.
It follows last week's move to cut 1,200 jobs and restructure its operations in Australia.
AMP has also scrapped plans to move its financial services arm into Europe after Italy rejected its bid due to regulatory concerns.
S&P said the writedowns were "outside that contemplated by recent rating actions. Following today's announcement by AMP, Standard & Poor's will assess the extent to which the group's medium-term earnings prospects and capitalisation remain congruent with existing ratings."
AMP's plans did not include the restructuring costs of the UK businesses, it said, which face further upheaval when AMP reveals its strategy for the operations next month.
The UK Pearl insurance business has already cost the company. AMP was forced into a A$1bn (£356m) equity raising recently.
