A Tinetti spokesperson said they became aware of the post within an hour of it being up, and took it down immediately.
An Electoral Commission spokesperson said in a statement, " I can confirm we became aware of the posts earlier today and contacted the Labour Party. The posts were taken down."
National's Sam Uffindell was crowned the city's new MP on Saturday night after he won the by-election's preliminary votes with a 6038 majority.
Uffindell had more than twice as many votes as Tinetti, finishing the count with 10,931 compared to Tinetti's 4893.
Asked if the Tauranga byelection was a "drubbing" for the left, Prime Minister Jacinda Ardern told RNZ this morning the outcome for Tinetti was one of Labour's better results in Tauranga for decades.
Byelections weren't the same as general elections, she said. "I'm not quick to read into general outcomes."
"Byelections, it is a bit hard to extrapolate too many lessons from them."