Mr Jennings left his bike and crossed over "keep out" barrier tape and told the contractors and a security officer that he would not leave the area and wanted to speak with a council representative.
"They have got to stop doing this - you can just go and knock trees like this down without talking to people about it."
He was told by a police officer, who contacted council management, that the trees were being removed to make a rampway for wheelchair access to the gardens and waterfront walkways.
"Wheelchair access is a great thing and I absolutely approve of it but they could put it somewhere else - there's plenty of space."
While one palm had come down he said there was no need for the second one to fall and hoped council staff would reconsider it.
Mr Jennings later met with council representatives about the work.
Council chief executive Wayne Jack said the meeting was to inform Mr Jennings about the work and to "alleviate his concerns".
Mr Jack said the trees needed to be removed in order for the Marine Parade traffic calming and pedestrian safety project to move ahead and that the planning team had engaged widely with any affected businesses about the progress of the plan. Mr Jennings has been invited to discussions.
Mr Jennings said his understanding had been that no actual physical work would begin. The road changes had been laid out with only markings to begin with.
Of the area where the trees are targeted, he said, he had formally asked the council to redesign what they were intending to do there.
Mr Jack said the trees, planted in the 1990s, were not listed in the district plan as trees of significance and that given their age and condition they needed to be removed.
Their location was a "tricky place" for root development which could eventually see them become a liability.
"They just need to redesign it - that's my take," Mr Jennings said.
The contractors had moved off the site just after 10.15am and the job was effectively on hold for now.