The offer would represent a a multiple of about two times Fairfax NZ's annual earnings before interest, tax, depreciation and amortisation.
A commission spokesman says the regulator was told about the potential buyer by Fairfax this morning.
Fairfax confirmed the offer in a statement to the ASX.
"Following media speculation today, Fairfax confirms that it has recently received a letter from a third party claiming that it has a client that would be interested in considering the acquisition of the Fairfax New Zealand business."
"The name of the client is not disclosed. The letter contains no offer capable of acceptance and Fairfax is not engaged in any discussions in relation to the letter."
Fairfax said it had a binding merger agreement with NZME, which included exclusivity provisions preventing either party from entertaining any offer from a third party in relation to the business and assets.
"Consistent with its exclusivity obligations under the MIA, Fairfax is continuing to work with NZME to satisfy the conditions under the MIA and is not engaged with any third party," the company said.
Shares in Fairfax last traded at 86.5 Australian cents on the ASX, and have shed 6 per cent this year.
NZME shares last traded at 55 cents on the NZX, and have dropped 31 per cent this year.
NBR reported a source saying that one likely buyer was private equity.
One private equity expert told the Herald there was always speculation that private equity were sniffing around any asset that was going through change.
But said he had not heard anything about it through industry sources and had only seen media stories on it.
"You certainly can't rule it out."
New Zealand has a relatively small private equity market which could indicate interest from overseas.
Fairfax Media chief executive Greg Hywood told the Commerce Commission hearing yesterday that it would "become endgame" if it did not allow a merger between Fairfax New Zealand and NZME to go ahead.
"We don't have the capacity of deep pockets of private money to subsidise journalism," said Hywood. "There are many proprietorial models where wealthy individuals and families, for social and political influence, own media companies, but we have shareholders and they demand that these publishing businesses stand on their own feet."
On the other hand, listed company status was a protection against loss of editorial independence, said Hywood, who was in Wellington for the second day of the Commerce Commission's public hearings into the proposed media merger, which the commission rejected in a draft determination last month, fearing loss of media plurality.
Yesterday's hearings concentrated on the impact of the merger on media plurality - the range of opinions, issues and approaches to coverage that the two news groups currently produce. Unquantifiable detriments to media plurality outweighed the clear commercial benefits of merging, the commission found.
Both publishers say a merger is essential if they are to survive commercially.
-additional reporting Businessdesk
