"The total debt held by Dubai Inc could well be in the range of $130-170 billion," the bank said in its 2010 UAE Yearbook, a copy of which was received by AFP today.
Dubai Inc is a term used to refer to the Dubai government and its government-related entities.
Dubai shook world markets in November when it said it wanted to request a freeze on debt repayments by its largest and most-indebted conglomerate, Dubai World.
At the time, Dubai's total debt, including that of its state firms, was reportedly $80 billion, with Dubai World owing $59 billion.
EFG Hermes said it estimated Dubai Inc's capital market debt, including bonds and syndicated loans, to have risen to $96.6 billion in 2009, including funds raised by the government to meet debt obligations.
But it pointed to upside risks, which could take the total debt to $170 billion, highlighting a lack of data on bilateral loans between Dubai Inc and banks.
"Bilateral lending... is a bigger concern to us since the scale of lending could be very large and data are practically non-existent," the bank said.
It estimated that the local Emirates NBD bank alone has roughly $24 billion in bilateral loans to Dubai Inc.
It also warned that there could be some capital market debt that is unaccounted for.
Meanwhile, EFG-Hermes said voluntary restructurings of Dubai Inc's debt are likely, as around 75 per cent of Dubai Inc's debt, which falls due in 2010-2011, is from syndicated loans.
"The creditors involved are a limited number of banks, which will most likely take a relationship-based, long-term view of these liabilities. Therefore, we expect a high degree of voluntary restructuring," it said.
Last month, international fears loomed over Dubai's ability to repay maturing Islamic bonds worth $4.1 billion owed by Dubai World's property arm, Nakheel, when they were due on December 14.
But the payment was made thanks to last-minute financial aid extended by oil-rich Abu Dhabi.
Dubai World has already started negotiations with its creditors to restructure the debt of its troubled subsidiaries, amounting to $22 billion.
Abu Dhabi has so far pledged $10 billion to help fellow emirate Dubai sort out the debt problems of its firms, in addition to $10 billion made available by the Abu Dhabi-based central bank of the United Arab Emirates.