Life insurers hold $321 billion in affiliated investments and about half of them belong to 10 insurers that have relationships with private-equity companies, according to a report Thursday from the National Association of Insurance Commissioners.

The group, which is made up of the top insurance regulator in every state, classifies investments as affiliated if they are backed by or sold by companies related to the insurer even if the related company is not the one on the hook for payments. Such holdings have grown as private asset managers have bought up insurers and sold them private credit and other alternative investments to put in their portfolios.

Affiliated investments tumbled into the spotlight this summer after two insurers controlled by Dodgers owner Mark Walter revealed that they had discovered, after receiving federal subpoenas, that they had failed to properly disclose a combined $20 billion in such holdings.

Insurers with some of the highest concentrations of affiliated investments include Security Benefit, Athene and Commonwealth, The Wall Street Journal has found. The NAIC found most life insurers have very limited affiliated investments. Industrywide, the share is about 5%.

In its report, the NAIC found the highest dollar amount of affiliated holdings-$188 billion-fell into the category of "other long-term investments" and the second-highest-$76 billion-was in asset backed securities. The 10 private-equity linked life insurers accounted for 95% of the affiliated asset-backed securities, the report said.