Cardiff Coal Exchange plan unacceptable - Victorian Society
A conservation group has "strongly objected" to plans to convert Cardiff's historical Coal Exchange into a hotel.
The Victorian Society has criticised an "almost total lack of detailed information" in the £40m proposals and urged Cardiff council to reject them.
Developer Signature Living has already started recruiting for 100 jobs and hopes to start work soon.
It said it had a "credible plan" and called the society's response "incredibly disappointing".
The disused Grade II*-listed building in Cardiff Bay dates to 1883 and is where ship owners and coal traders once met.
The world's first recorded £1m deal was struck there in 1904.
It has been used as a music and events venue in recent years, but closed in 2013.
Plans to convert it into a 200-bedroom hotel were unveiled in April.
An application for a change of use is due to go before the council's planning committee next week, and the developer said it would host weddings and conferences if given planning permission.
The full detailed plans will be decided upon at a future date, while discussions are ongoing between the developers, Cadw and planning officials.
But the Victorian Society's senior conservation adviser James Hughes said it was "simply not credible to suggest, as the submitted drawings do, that no alterations or structural interventions are to be made to the fabric of the Coal Exchange".
In a formal objection, he also questioned the lack of detail about heating, lighting, en-suites and lifts.
"No details are provided as to how the highly significant historic fabric and various spaces are to be altered or adapted, if indeed they are to be.
"How will the windows, the floors or the fine timber panelling - to name just a few - be treated and what will be the impact on the exceptional significance of the listed building?"
He described the lack of detail available to scrutinise the proposals for what is one of the most significant buildings in the country as "simply unacceptable."
Mr Hughes told BBC Wales the society first met with the council two years ago when the building was said to be in danger of collapse but there was no survey or conservation plan available - and none had been produced since.
He said it was incumbent on the developer to provide one, as well as details of how it intended to save "one of the most important buildings in Cardiff and Wales".
Campaign group Save the Coal Exchange has also said it could not fully support the plan until it had seen details about preserving the building.
A Signature Living spokesman said: "It is incredibly disappointing that the Victorian Society would rather see the Coal Exchange rot and not be saved.
"Signature Living has a credible plan to save the historic building and put it back into use.
"The concerns raised by the society do not reflect the plans Signature Living have for the building - we have already started recruiting staff and intend to move forward with the project.
"I'm sure when we have finished the Victorian Society will agree that we have not only saved a historic building but preserved it for years to come."