In a statement, Mr Tong has confirmed he is among the prosecution witness for a trial about both National and Labour Party donations in Auckland.
Mr Tong released a statement last week saying his involvement was due to his relationship with New Zealanders Colin Zheng and Yikun Zhang, both of Auckland, who were were appearing in the High Court facing charges laid by the Serious Fraud Office.
Charged along with them are former National Party MP Jami-Lee Ross and others.
Mr Tong said he provided evidence for the prosecution to the Serious Fraud Office in 2020 but up until now had not been in a position to release any information.
"While I cannot go into detail — I want to be as transparent as possible and as upfront as I can be at this time ...
"I am not in a position to release any information regarding that evidence; however, I have been authorised to advise that I was never a suspect in this matter."
He had been summonsed by the prosecution to give evidence and that would happen in the next three weeks, he said.
Seven people are facing charges laid by the Serious Fraud Office in relation to two cases that are being heard together.
At the first day of the trial, Crown prosecutor John Dixon said the cases concerned three separate donations in which sham donors concealed the true identity of the actual donors.
The trial in the High Court at Auckland started on July 26 and was set down for 10 weeks.
Mr Tong is running again for the Southland mayoralty.
He had announced he was running for the Invercargill mayoralty but changed his mind a few weeks ago and switched back to seeking re-election.
Staff Reporter
