Hamilton Mayor Bob Simcock is defending the use of anonymous donations to fund his re-election campaign.
A lawyer and opposing candidate, Julie Hardaker, says half of his $50,000 campaign is being paid for by anonymous donations.
Donations of less than $1000 are legally allowed to be made anonymously.
But Ms Hardaker says the problem is one of perception.
Mr Simcock says his use of anonymous donations is deliberate: he insists on anonymous donations, so that no one can try to influence him.
He says his lawyer is responsible for his fundraising, and he does not know the details of it.