The trust wanted the letter, in which it said it would have difficulty working with EnviroWaste, one of the prospective contractors tendering for the contract, before councillors ahead of yesterday's council meeting.
However, Mr Ross made the decision not to distribute the letter after taking legal advice and consulting Mayor Alex Familton.
Mr Ross told the Otago Daily Times yesterday the trust letter arrived on Friday, addressed to Mr Familton but with a request to distribute it to councillors.
He sought legal advice on the letter and was told that it could influence the process of awarding a contract.
The council could then face legal action from one contractor, EnviroWaste, if it decided to award a contract to the other contender, Delta Services.
EnviroWaste could sue for the costs of being involved in the process and preparing a tender.
The first request for proposals sent out to prospective contractors - including the trust -stipulated there was to be no lobbying in relation to the contract.
The trust indicated in February it could work with both contractors, but was now saying it would have difficulty with EnviroWaste, he said.
In its letter, the trust said it would have difficulty working with EnviroWaste because the principles of the two organisations were too broadly opposed.
"Clearly, they are not interested in forming a mutually beneficial working relationship with the trust,'' it said.
The trust could not work in conjunction with a co-mingled waste system, where recyclable materials were collected mixed together and it strongly urged the council to cancel its waste management process and start again.
