Lumley has reacted to concerns about its listed parent Wesfarmers' proposed acquisition of Coles by promising to "ring-fence" its credit ratings.

Lumley General Australia and Lumley General New Zealand currently have an A- credit rating with Standard & Poor's.

Wesfarmers' $20 billion takeover bid could lead to a reappraisal of the diversified company's credit rating. But Wesfarmers Insurance Division MD Rob Scott says ring-fencing the insurance operations will provide clients with reassurance.

He says the group "is aware of the importance to many of our customers of a strong credit rating for our insurance companies".