Ladner also said Sullivan lacks public support and the confidence of voters.
In front of a huge throng of media, Ladner delivered a clear message - Sullivan must go.
"Overall I feel the mayor has lost the confidence of voters," Ladner said in response to questions. "I haven't seen any evidence, whether from a poll or people on the street, to say there's strong support for the mayor."
"When I'm part of a team and I see the ship headed for the rocks, I feel an obligation to change course," Ladner said.
Ladner, in his second term as councilor, refused to speculate on whether he would run as an independent candidate for mayor if NPA members refuse to open up the nomination process at an Annual General Meeting scheduled for April 22. But he did not specifically rule it out either.
Currently the NPA "green light" policy protects all incumbents from nomination challenges provided they meet criteria set by the party. Ladner wants that policy overturned by the membership, which would have to open all nominations to competition, not just the mayoralty nomination.
In his prepared statement Ladner said he wants to end the "petty bickering that has characterized city hall" and put the non-partisan back in the Non-Partisan Association.
Vision Vancouver councilor Raymond Louie and Sullivan spokesperson David Hurford, although speaking separately after the event, had similar perspectives.
"Councilor Ladner has the same voting record as the mayor," Louie said.
Hurford echoed that. "Councilor Ladner has voted with the mayor on every major issue," he claimed.
But earlier Ladner spelled out what he saw as several differences with Sullivan, saying he opposed the mayor's controversial personal trademarking of the term "eco-density", that he supported returning savings from last year's bitter CUPE strike to taxpayers while Sullivan did not, and that Sullivan voted against the downtown eastside Woodward's project while Ladner supported it.
Hurford said Sullivan retains solid support from NPA elected officials.
"The caucus members, other than Mr. Ladner, are supporting the mayor," he told reporters.
But several NPA elected officials have called for an open nomination process, including Park Board Commissioner Ian Robertson and School Board Trustee Eleanor Gregory.