Belfast's HMS Caroline could be towed back to Portsmouth "for its own protection" within the next year, it has emerged.
Dr Tim Schadla-Hall, the chairman of the HMS Caroline Preservation Society, warned the First World War ship was at risk in a letter to Economy Minister Diane Dodds.
He said that with the vessel to remain closed until next year because of the coronavirus pandemic, its future as a tourist attraction was in doubt.
Dr Schadla-Hall added that if it was not allowed to reopen within the next four to six weeks, the National Museum of the Royal Navy may be forced to intervene and return it to Portsmouth.
The Executive wants to keep HMS Caroline closed while studies are carried out, but Mr Schadla-Hall maintained that these could be completed while it was operational.
"Lockdown has already seen the underwater hull survey delayed and no real maintenance conducted as all other staff are and remain furloughed and contractors have been subject to the range of restrictions in force," he explained.
"My greatest concern is that the material state of both the ship and its interpretation will deteriorate - and this will inevitably cost more to put right."
It earlier emerged that there were "significant concerns" over potential contamination to the hull of the ship and silt at Alexandra Dock, where it is berthed.
Taxpayers would have to meet the cost of any operation designed to tackle the problem.
Despite the mounting list of issues, Mrs Dodds said she was determined to find ways to keep the important museum afloat.
In a written Assembly answer to Ulster Unionist Party leader Steve Aiken, the minister added: "There were significant concerns regarding potential contamination to the ship's hull and in the silt at Alexandra Dock following specialist surveys.
"There was the potential risk of the main shipping channel becoming contaminated, potentially meaning its closure to allow for an expensive clean-up operation."
The concerns around contamination previously led to delays in the signing of an agreement on management of the ship with Belfast Harbour Commissioners.
The deal, which is less than a decade old, was struck when the Department for the Economy was known as the Department of Enterprise, Trade and Investment.
In 2012 the National Museum of the Royal Navy developed HMS Caroline as a maritime heritage visitor attraction for the department, funded by the National Lottery Heritage Fund and Tourism NI.
They then provided additional grants when the scope of the project was widened and implemented two years ago.
But the present agreement expired on June 30, giving insufficient time for the department to put in place a new funding model, operational agreement and operator.
"Additionally, visitor numbers have been disappointing, resulting in substantial operational deficits," Mrs Dodds admitted.
Describing the situation as a "debacle", Mr Aiken said: "That the minister is shutting down the ship at the same time as her own department attempts to maintain and bolster our Northern Ireland tourism and visitor attractions simply beggars belief.
"Next year will probably be marked by HMS Caroline being towed away to Portsmouth.
"It's not the start to Northern Ireland's centenary year we hoped for."
The ship has been an integral part of Belfast's dockland since 1924.
It is second only to Lord Nelson's HMS Victory, which saw action in the Battle of Trafalgar, in terms of its historical significance.
The National Museum of the Royal Navy and the Department of Enterprise, Trade and Investment agreed in 2012 to embark on a campaign to save the ship from being scrapped.
They eventually secured funding for the most complex maritime restoration project ever undertaken in Ireland.