Its main benefactor has suddenly up its contribution to £35 million after it emerged the overall cost had soared to at least £70 million.
Earmarked for a site off St Andrew Square, project has £25 million worth of support confirmed from the UK and Scottish governments and the city council in place. A £10 million fundraising campaign was launched two yeas ago.
The soaring cost is the second major blow to hit the project in a matter of weeks after it emerged that the developers of a nearby hotel and retail development have launched a legal challenge against the 1000-seater venue, which will provide a new home for the Scottish Chamber Orchestra and the Edinburgh International Festival.
The Dunard Trust, which has pledged to underwrite the project, has not publicly revealed the extent of its backing before now, although it was understood to be in the region of around £10 million due to the pledges of public funding on the table.
The Dunard Trust said it had “confidence” that the additional funding would allow Impact Scotland, the charitable trust pursuing the project, to “meet its goals.”
However an official new cost for the first new concert hall to be built in Edinburgh for a century, will not be known until next year.
The Dunard Centre, which is to be named after the family trust overseen by American arts philanthropist Carol Grigor, received planning permission in April. Impact Scotland confirmed that it was currently working with the contractor to “revise costs from early initial estimates.”
A spokeswoman for Impact Scotland said substantial work had to be down to keep the height and mass of the building down to ensure it could secure planning permission. The venue will also have a much deeper basement than originally anticipated.
A statement from Impact Scotland said: “We’re currently at the stage of working with our contractor to revise costs from early initial estimates.
“We have made considerable enhancements to the building during the design development stage, not least to address heritage concerns enabling us to be granted planning permission.
“The end result will be a better building - a game changer for music and performance in Edinburgh.
“Revised costs will be available following the completion of the pre-construction period next year.
"We are pleased to have received this increased pledge from Dunard Fund which demonstrates their huge commitment to the creation of the new venue and provides the cost flexibility required for such an important project."
A spokeswoman for the Dunard Fund said: “We are delighted to confirm that Dunard Fund has offered to increase its pledge of support to £35 million.
"This must represent one of the largest funding offers from any one Scottish charity to another.
“We are extremely enthusiastic about the performance hall, which recently received planning permission, and that with the additional funding pledged, we have the confidence that Impact Scotland can meet its goals.”