Inspector Alisse Robertson of the Auckland police said officers and partner agencies had been attempting to work with the hikoi group.
"While we respect any person or group's right to lawfully protest, we must also balance this with public safety," Robertson said.
"Walking across the Auckland Harbour Bridge poses significant risk to motorists and the individuals themselves."
Robertson said the group had not submitted a formal application to the Transport Agency - although the agency had advised any request would not have been approved due to safety concerns.
Robertson said: "The group has chosen to ignore this advice and despite numerous attempts by police staff to look at alternative options, they have refused to negotiate."
Any protesters who did venture over the bridge on foot could be fined or arrested, and charged with endangering transport.
Robertson added that resourcing a police team to control the protest took staff away from being out in the community, preventing crime.
It was "very disappointing", she said.