The meeting was not publicly notified, media were not informed it was taking place, and councillors were given only 24 hours to consider the submission.
"At no point had the council discussed lodging a joint submission. We had very little time to consider what was a poorly written, negative document that we had no input into," said Mr Sharp.
"I'm disappointed and embarrassed that it was lodged, the council did not have a mandate from the community to approve this, but the vote was such that I have to accept it."
Initially told it had been written by Mr Jack, he said further inquiries revealed it was the work of an independent person, the identity of whom "no one can tell me".
Councillor Terry Kingston also cited lack of time as his reason for voting against the submission.
"We only had 24 hours notice - the mayor did not break any rules by calling the meeting as he did but I would not have handled it the same way, especially in light of Mr Story being absent."
Councillors Kelly Annand and Andrew Watts also voted against the submission. Councillors Mark Williams, Sally Butler and Maitland Manning were in support.
Mr Williams said he thought CHB should show solidarity with the two other councils after an unofficial meeting was held in Napier about the Local Government Commission's proposal soon after it was released last year.
This week he could not remember exactly who was there from Central Hawke's Bay.
"We agreed then to lodge a joint submission - I appreciate the short time frame was unfortunate, and I'm not sure why it took so long to reach our council to deliberate on, but I thought it would have looked peculiar if it was just a Napier and Wairoa submission when our mayor has been quite vocal about amalgamation."
Mr Sharp said he did not attend that meeting in Napier and the prospect of lodging a joint submission had not been brought to the full council to discuss. Mr Butler said proper procedures had been followed giving 24 hours for the extraordinary meeting and his use of his casting vote, which in effect gave him two votes.
"Everything was above board - it was short notice because of when the submission came to us.
"I gained 700 votes when I was successfully re-elected for a second term and I believe that gives me a mandate to vote the way I did."
Napier city councillors voted to adopt the joint submission on March 5 at the same meeting where they signed off on their own submission.
Wairoa Mayor Craig Little said his council had also voted to adopt the joint submission.