Less than a month before the Rena ran aground off the coast of Tauranga last October, a similar-sized container ship passed about 1.5 nautical miles from the same reef.
The revelation comes a day after a Transport Accident Investigation Commission interim report into the grounding of the Rena showed shortcuts were taken.
The New Zealand Nautical Almanac says 3 nautical miles is the recommended safety zone oil tankers need to keep away from Astrolabe reef, although Maritime New Zealand says there was no exclusion zone for container ships.
A marine consultant John Riding says on 15 September the Cap Mondego sailed about 1.5 nautical miles from the reef.
The Cap Mondego is 231 metres in length, the Rena was 236m.
He says his records also show other ships travelled close to the reef in the month before the Rena ran aground.
"Probably 70% of the traffic that was heading into the Bay of Plenty cut too close to the reef, well within the three mile criteria that's been set."
Mr Riding says that represents about 50 ships.
He believes there should be mandatory routes, which ships must take, in areas with hazardous points.