"This was a public submission. This has been an eye-opener into how some councillors behave during the democratic process," Mr Smith said.
"Many people took time off work to come down and support the petition - now we have to do it again."
Mr Vinsen later told the Chronicle he did not believe that supporting the TPPA group was "local government business".
He said: "I trust this current Government to negotiate in our best interests on this treaty."
Ms Main told the supporters she was "really disappointed" with the action of the four councillors.
"I apologise to you all on behalf of this council because I believe you have valid concerns."
She assured the group that the matter would be back on the council agenda at a future date.
Three speakers represented the petitioners. David James said they wanted the council to take a leadership role and take their concerns to central government.
Mr James said the treaty represented a sell-out to major corporations which could have a huge effect on Wanganui's community and economy.
Auckland, Nelson and Tasman councils have adopted the resolutions while others have accepted them partially.
Mike Nixon said the agreement meant even councils such as Wanganui's "could be bullied by big corporations".
Councillor Hamish McDouall said the council had the chance to show democracy at work by supporting the petitioners.
Councillors Sue Westwood and Rangi Wills were absent from all council meetings yesterday having earlier tendered their apologies.