It follows an earlier letter from council chief executive Stephen Town asking ACIL to "encourage" court bosses to halt the extensions until a wide-ranging port study is done.
"I want to make it clear that I am continuing to emphasise, to both ACIL and Ports of Auckland, the need for pace and certainty in their decision making.
"We, as a council, and the people of Auckland need to have clear air to enable a mature public conversation to take place about the future of the port in Auckland," Mr Brown said in his memo.
The letter from ACIL to ports follows the tone of the letter from Mr Town to ACIL, suggesting construction stop on the extensions pending the outcome of the port study.
The ACIL letter to ports chairman Graeme Hawkins said the council body was concerned that the ports company believed an engagement programme would not affect the timing of contract works for the wharf extensions.
"The ACIL board expects that the Ports of Auckland board has made its decision in relation to this work with due regard to the economic and financial interests of the company, its shareholder and the people of Auckland.
"However, we are concerned that the decision may not have properly recognised Ports of Auckland's wider commercial responsibility to appropriately manage all stakeholders' interests, including, most importantly, those of the people of Auckland," said the letter, written by ACIL chief executive Gary Swift.
He said ACIL had no legal power to direct the ports board in operational issues, but "nevertheless we strongly suggest that no further physical works be undertaken on the wharf extensions until such times as a meaningful dialogue with the people of Auckland can occur".
The wider study, into the economic, environmental and social impact of the port on the wider city, is expected to take 12 months. Work has started on the design of the study.
The Herald understands that main construction work on the two wharf extensions at the end of Bledisloe Wharf has been put on hold while the discussions continue between ACIL and the ports.
Enabling works have started on the extensions. A subsidiary of Fletcher Building, Brian Perry Civil, has the contract for the main works.
Ports spokesman Matt Ball said main works could start this month or next month.
Councillor Mike Lee said the council was constantly sending mixed signals to the port.
"It has lurched from nod nod, wink,wink approval to a supposed 'thermonuclear option' and now seems to swinging back to be concerned about the 'pace' of the decision, rather than the decision itself," he said.
Stop Stealing Our Harbour spokesman Michael Goldwater said considering the public uproar it was the right decision by the ports company to put the extensions on hold.
"It's about time they listened to what Aucklanders want," he said.
The right-leaning councillor for Orakei, Cameron Brewer, said the port company should respond swiftly and positively to the ACIL letter.
"We all now wait with bated breath as to the Ports' formal response. Surely with a majority of the public, the mayor and councillors, and now their direct bosses at ACIL all calling for tools down, they have nowhere to hide.
"I encourage them to respond swiftly and positively. Their defensive PR campaign has failed them badly and changed no ones mind. They now need to come out of the bunker waving a white flag. Whether they like it or not it's there only option," Mr Brewer said.
Mr Swift said the letter from ACIL to the port was a commercial matter and while the council body did not feel it was up to it to release it "we have no objection to the mayor doing so".
"In terms of ACIL's ongoing discussions with Ports of Auckland, we understand the Mayor's concern, and indeed are working as hard as we can to resolve the matter as quickly as possible," he said.
The right-leaning councillor for Orakei, Cameron Brewer, said the port company should respond swiftly and positively to the ACIL letter.
"We all now wait with bated breath as to the Ports' formal response. Surely with a majority of the public, the mayor and councillors, and now their direct bosses at ACIL all calling for tools down, they have nowhere to hide.
"I encourage them to respond swiftly and positively. Their defensive PR campaign has failed them badly and changed no ones mind. They now need to come out of the bunker waving a white flag. Whether they like it or not it's there only option," Mr Brewer said.
Mr Swift said the letter from ACIL to the port was a commercial matter and while the council body did not feel it was up to it to release it "we have no objection to the mayor doing so".
"In terms of ACIL's ongoing discussions with Ports of Auckland, we understand the Mayor's concern, and indeed are working as hard as we can to resolve the matter as quickly as possible," he said.
