Smith is now on unexplained leave.
The council has been holding all its discussions about potential rate increases and its long-term plan, in workshops closed to the public and reporters.
But a letter written by Smith and leaked to the Greymouth Star cites a proposal for a 30 per cent increase in regional rates this year.
Smith wrote he had "just got the council over the line with the LTP numbers" even thought it was well behind schedule.
"It was resolved, 30 per cent (rate increase) for the first year; 10 per cent in years two and three and five per cent for years four to ten.
"Huge effort was required and to be fair, it almost broke me", Smith confides in the letter.
The council is facing steep cost rises and a need for more staff to deal with a growing workload, largely blamed on the Government's new environmental rules.
Asked about the apparent behind-the-scenes struggle, Cr Birchfield acknowledged he had been holding out for a rate increase of between zero and 5 per cent.
"People can't afford big increases and I felt there were other things we could do, like sell our quarries and put up user-charges.
"But the risk was if we didn't agree to the 30 per cent we could have ended up with a commissioner running the council … that was what we were facing."
The rate rise still had to be consulted on but should be reviewed, Cr Birchfield said.
Vin Smith has not been available for comment; his answerphone says only that he is "on leave".
The draft LTP with its bombshell rate proposals are set to become public at the council meeting in June.
By then Cr Birchfield may no longer be at the head of the table.
An extraordinary meeting to remove him as chairman has been advertised for May 31.
The four councillors who called the meeting look set to outvote the chairman and his two supporters - unless one of the four changes their mind.
They are deputy chairman Cr Stuart Challenger, Cr Deborah Magner, both from Westland, and Buller councillors Laura Coll McLaughlin and John Hill.
Cr Hill, whose sole vote secured the chairmanship for Cr Birchfield after the 2019 local body election, said he had supported the call for the extraordinary meeting, but felt councillors should not be commenting publicly before then.
"It's unfortunate that it takes so long (until May 31) but that's the notice required by the Local Government Act," he said.
Cr Birchfield, who was the highest polling candidate in 2019, said he had been getting calls of support but was not optimistic about his chances of keeping the position.
"They've got the numbers, or they wouldn't have called the meeting."
