Christchurch City Holdings wants to increase its stake in Lyttelton Port, in the hope of being able to delist the company.
It currently holds 75.68% of the company and is offering $2.75 per share for another 2.48%. The offer is 50 cents above Wednesday's closing price.
Christchurch City Holdings chief executive Bob Lineham, says it can't buy more shares without being forced to make a full takeover offer under the Takeovers Code.
He says there would be no point in that because Otago Regional Council holds a blocking stake, but if the current offer is successful, it could apply to delist from the exchange.