"Do reprimand the brokers who look to secure prices through means outside the accepted business norms," he told the Planters' Association, representing big corporate tea producers at its annual general meeting.
"This will have a positive impact on performance and very importantly eliminate any risk of defaults against your proceeds."
It was also important to ensure brokers are given clear direction of services expected of them.
His warning came in the wake of the Colombo Tea Traders' Association tightening its bylaws to ensure greater discipline at the auctions.
Ramanayake till recently was the head of John Keells tea brokers and a broker with long years of experience.
He said that the auctions were until recently the ideal platform of sale with demand from around world focussed on Colombo to a much greater extent than in other auctions in producer countries.
"Teas of each producer, whether large or small, get equal attention based on the parameters of quality, thus creating a level playing field," Ramanayake said. "There is a set off bylaws that bring stability to the process."
However, he said, "more recently the unprecedented volume of private sales and flexing of the bylaws have prevented the total benefit being derived from our auction system."He urged the plantation firms to "make critical evaluation of the current situation and bring in prudent controls to derive the benefit of the excellent structure that is available."