Internal police documents recently released under a parliamentary order revealed the officer lodged an insurance claim that said the May crash happened while he was travelling through Sydney's NorthConnex tunnel and the driver "fell asleep".

"Vehicle veered off roadway, colliding with a crash cushion," the form said.

"Vehicle was still driveable so vehicle driven from scene."

Officers investigating the incident later told the insurance company the driver had been drinking alcohol before the crash and the damages claim, worth $40,955, was refused, emails showed.

The high-ranking officer had allegedly been drinking at a function before getting behind the wheel of a police-issued car in the lead-up to the incident.

Another senior officer expressed concerns about the insurance form in a September email, noting the document included no mention of alcohol.

"In my view the claim in (its) current form is one submitted in bad faith," he said, noting the officer had been told two months earlier that charges were likely.

The high-range drink-driving charge carries a maximum jail term of 18 months.

The matter has been referred to the internal Professional Standards Command and the independent police watchdog, the Law Enforcement Conduct Commission. 

The officer's employment status is also under review.

NSW Police Commissioner Karen Webb previously said she had been aware of the incident since May and the officer had been charged after a "lengthy and comprehensive" investigation.

She denied there had been any attempt to cover up the allegations in the failure to issue a public statement outlining the charges, describing it instead as something that "slipped through the cracks".

The accused officer, known only as AB because of the suppression order, is due to return to court in February.