A Moody's report into finite reinsurance said making the tool transparent would determine its legality.
The report, Understanding and Evaluating Finite Reinsurance, claimed US investigations are looking at whether companies have properly accounted for their finite reinsurance contracts.
It also said the probe questioned whether the product was used to smooth earnings or to mask other adverse financial trends.
The report's author, vice president Chris Hall, said: “The general lack of transparency has made analysis of this type of instrument quite challenging and, in some cases, even impossible."
Hall said making finite reinsurance contracts transparent would help to determine whether financial statements had been affected.
