Under the Protected Objects Amendment Act, the museum is required to authenticate all artefacts brought to it by the public.
The Ministry of Arts, Culture and Heritage pays the museum an annual grant to do so.
However, the museum has long argued the payments are inadequate.
Mr Paul told the museum trust board this week that a letter from the ministry offering a $7000 payment for the 2007-08 financial year, conditional on the museum accepting the same amount for each of the next three years, was "unacceptable and unethical".
There was "no way" companies which supplied services to the museum would accept such a condition, and the museum would not either, he said.
The board endorsed a strongly-worded draft letter to the ministry in which Mr Paul reiterated the museum's request for a payment of $15,000 a year, and rejected any attempt to tie the museum into a four-year contract.
Mr Paul said yesterday the issue would be discussed at a meeting between the museum and the ministry next week.
If there was no satisfactory outcome, he would send the letter and instruct his staff to cease authentications.
Asked if that action would inflame the dispute, Mr Paul laughed.
"I don't think so. The situation is already as inflamed as it can be . . .
"If they think $15,000 a year is unreasonable, they can take their work elsewhere. They would have to employ a consultant, and how much would that cost?"
Mr Paul was not hopeful of a successful outcome.
"I will be very surprised if they change their stance. But who knows? They might surprise us," he said.
Ministry chief executive Martin Matthews said yesterday the ministry had made a "really generous offer as a contribution to the museum's fixed costs".
"For the level of activity involved, we believe they are more than adequately compensated," Mr Matthews said.
Asked what would happen if staff were instructed not to authenticate items, Mr Matthews replied: "That is a good question, and one which we will address if it happens."
Entering into multi-year contracts with museums was "not unusual", he said.
The Canterbury Museum had recently signed a similar four-year contract for its authentication payments.
