The study by commercial real estate services firm CBRE comes just days after Hong Kong announced its first residential property tax targeted at overseas buyers as U.S. quantitative easing and record-low interest rates boost the risk of a housing bubble in the Asian financial centre.

"Hong Kong is at risk of choking itself at future economic growth and prosperity because it's not delivering the office space to satisfy the demand," said Craig Shute, senior managing director at CBRE.

The forecast shortfall in office space comes even as global companies pull out of traditional core business areas in Hong Kong to cut costs as lingering economic uncertainties take a toll on firms in the world's most expensive office market.

Hong Kong is 11 percent more expensive than London's West End, which ranks second globally, and 33 percent ahead of Tokyo, which is ranked third, according to CBRE.

KPMG, one of the big four accounting firms, recently relocated from the upmarket Prince's Building in Central district to the busy shopping area of Causeway Bay.

Royal Bank of Scotland Group PLC (RBS.L) has also moved staff from Cheung Kong Center, the headquarters of Asia's richest man Li Ka-shing, to less costly properties.

CBRE said Hong Kong's estimated pipeline of 8 million square feet of office space by 2020 falls short of a total 17 million sq ft forecast to be needed by then based on projected GDP growth.

"There is currently an imbalance, whereby space is mostly available at the top end of the market but demand is now driven by cost-saving practices," CBRE said in the report.

While commercial leasing is now concentrated on lower-cost locations, prices in many of the non-core areas are climbing steadily as demand increases.

"Outside Central, the rents continue to increase and vacancy is extremely low," said Shute. "Vacancy is very tight and this situation is likely to intensify over the coming years."

In Central district, a hub for many multinationals, rents fell 1.2 percent in the second quarter of 2012, although the overall market still edged up by 0.1 percent, according to a study by global real estate services firm Jones Lang LaSalle.

Hong Kong has said it will take measures to curb prices in the commercial real estate market if necessary and the government announced on Tuesday it would discuss further steps to cool the overheated property market at a meeting on Friday.

In June, China outlined plans for a $45 billion economic zone in Shenzhen, about an hour by car from Hong Kong, in a move analysts said would give the city fresh outlets for expansion beyond the congested territory.

Hong Kong's main office developers include Sun Hung Kai Properties Ltd (0016.HK), the world's second-largest developer by market value, Swire Properties Ltd (0019.HK), Hongkong Land Holdings Ltd (HKLD.SI) and Wharf Holdings (0004.HK), the city's top mall operator. (Editing by Anne Marie Roantree and Jeremy Laurence)

• A Permanent Economic Emergency