The 15 cities surveyed are San Francisco, Madrid, New York, Singapore, Sydney, Washington, London, Mumbai, Tokyo, Mexico City, Paris, Hong Kong, Houston and Frankfurt.
According to the Knight Frank survey report, Mumbai which ranked sixth among global cities in 2007, slipped to the 10th position in 2014 mainly due to delayed revival of the Indian economy and lack of business confidence.
"While rental decline has been the primary reason, a depreciating rupee added fuel to the fire," Knight Frank Chief Economist and Director of Research Samantak Das said in the report.
Among the top 15 global cities, office rentals in Mumbai are lowest at Rs 250 per square feet per month, compared to London and New York which stand at Rs 900 square feel and Rs 360 per square feet respectively, the report said.
According to the report, current vacancy levels within the Mumbai office market lies at 23 per cent, which is the highest, as compared to the top 15 global cities.
However, rental yields within the city's office market, is the highest, at 10.3 per cent, as compared to cities like Sydney, Washington and Shanghai, which offer rental yields of 6.3 per cent, 6.2 per cent and 6 per cent respectively, it said.
However, in the coming years, financial services and banking occupiers to return to drive sizeable segments of demand, he said in the survey report.
