Grade-A office rents dropped 6.1 per cent in the second quarter of the year, bringing the decrease for the first half to 13.9 per cent, according to FPDSavills.
Central continued to be the hardest-hit district, with rents plunging by 10.4 per cent over the quarter, and 18.9 per cent over the first half, it said.
Demand had remained weak, resulting in rising vacancies and falling rents.
FPDSavills said vacancy rates in Central rose to 9.7 per cent at the end of last month. If sublet space was factored into the calculation, 'effective' vacancy rates were estimated at 12 per cent.