Keith Stewart found that the loch goes to a depth of 889ft (270.9m) on sonar equipment he uses.
The official maximum depth on the current chart for Loch Ness is 754ft (229.8m).
But the Maritime and Coastguard Agency (MCA), which is responsible for the official measurements, said it has no plans to resurvey the loch.
Mr Stewart's discovery has been dubbed a new hiding place for the loch's mythical monster, Nessie.
The MCA is responsible for mapping the sea and deep lochs and lakes around the UK.
It does this in order to maintain British Admiralty charts under the UK Civil Hydrography Programme.
An MCA spokeswoman said: "We currently have no plans to resurvey Loch Ness."
A tour boat skipper has recorded a new deepest point in Loch Ness on his vessel's equipment.