Plans have been drawn up, funding streams have been sourced but not confirmed, and a market manager is expected to be chosen by Christmas.
But fishermen say they have yet to see the evidence to convince them the scheme is viable for Newlyn.
The chief executive of the Cornish Fish Producers Organisation, which represents Cornish fishermen, said the question needs to be answered "sooner or later".
Paul Trebilcock said while all market users wanted to see improved market facilities, there was fear about the financial exposure and increased costs of landing fish in the port.
"Without clarification on costs we're in no man's land and unable to give the debate any meaningful contribution," he said.
"There's rumours but nothing factual to go on."
A harbour commissioner, who asked not to be named, said "surely it was the harbour commission that should be concerning itself with the figures".
"I don't know of any other company where the customer comes along and demands to see the company's figures.
"It's up to the commissioners to make the decision regarding the market and to endeavour to keep Newlyn market alive," he said.
The funding for the fish market is expected to be met via three separate pots.
The Harbour Commission is expected to put forward £2 million – the source of which has yet to be chosen.
The remaining £5 million is expected to be met by the European Fisheries Fund and the European Regional Development Fund.
The commissioner said: "As a commission we had a choice: we could have spent £8 million of our own money which we do not have on repairing the market we have.
"Or we could spend £2 million and get grants of £5 million to build a brand new market.
"We can only get grants if we build a new market."
David Stevens, skipper and owner of Crystal Sea, said fishermen accepted that without new facilities Newlyn's future as Britain's premier port was in jeopardy.
However, he said it was crucial fishermen were told the truth about the financial outlay and the perceived increase in landing costs.
"Why have we not seen a comprehensive business plan?" he said.
"We need to see the detailed accounts of the harbour now to see if they can afford it.
"We know we need improvements but we must be sure that £7 million for a market building is not too big a venture for Newlyn to afford."
Fellow fisherman Michael Williams said: "If we haven't seen a business plan how can this go ahead?
"That's what all the boats want to know."
The tender for the market building will be published in the European Journal next week and a decision is expected to be made before March.
article copyright THE CORNISHMAN