St Patrick's Centre faces closure on 30 April
The St Patrick's Heritage Centre in Downpatrick, County Down, is facing closure on 30 April.
The warning is contained in a briefing note prepared by centre staff and given to Down District Council and MLAs.
The note sets out funding difficulties following a series of cuts in the council grant and other changes.
It states the consequences of closure would be the immediate cancellation of all bookings from tour operators, including 252 coaches due to visit.
It warns that once these are cancelled it will be difficult to persuade these operators to return in future.
The funding problems include the removal of the centre's overdraft facility in February and a further reduction in the council's funding grant by £20,000 to £115,000.
The note states: "The centre cannot sign up to the annual service level agreement because it cannot deliver on the amount offered and on the advice of our auditors and legal team declare themselves unsustainable and set a date for closure to avoid trading illegally, April 30th."
VIP guests who were due to visit the centre include the Irish president and cardinal archbishop of New York.
Basil McCrea, the chairman of the assembly's employment and learning committee, expressed concerns there was a real danger the centre could close.
He said: "It should be borne in mind that St Patrick as a brand is just as big - if not bigger - than the Titanic. And we should be investing in this.
"And I'm quite sure the council will want to find as a matter of urgency a way to resolve this political difficulty."
The issue was discussed at a full council meeting on Monday evening.
The council is also due to meet the centre management for crisis talks on Wednesday.
A number of options will be proposed to ensure the tourist attraction remains open.
The chief executive of the centre, Timothy Campbell, declined to comment.
Other consequences of closure of the signature project and exhibition include the closure of the Daisies Cafe, with the loss of two permanent posts and employment for 18 local young people with special needs.
Closure would also mean the loss of £1.5m from the local tourist economy, the loss of £650,000 of direct and indirect support to local businesses and the removal of £36,000 in funding from the Department of Foreign Affairs to tackle sectarianism and promote reconciliation.
There are concerns that the St Patrick's Centre has faced cuts while millions have been poured into the Titanic project.
The centre generates income of about £190,000 a year on top of its £150,000 council funding, whilst building/running costs are around £314,000.
The centre said this compared favourably with other projects such as the Navan Centre and the Down County Museum.