Life insurance providers have revealed that some doctors are voluntarily sharing their patients' entire medical histories, even though they've only asked for information relevant to a claim.

Commonwealth Bank, ANZ and Westpac-owned BT Financial Group were among the big players that fronted a joint parliamentary inquiry into the life insurance industry in Canberra on Friday.

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MLC Life Insurance revealed it had started obtaining consent from new customers to access their full medical records from their doctor, though it conceded they probably weren't aware of it.

"Now they probably don't know that they've consented and I can see because it's in the contract that I'm sure many of them don't fully read," said its CEO David Hackett.