There is an icy wind blowing through Perth, with the CBD's office vacancy rates hitting a 20-year record high following crumbling demand just as new towers are getting finished.

The Australian Financial review reports the vacancy rate across Perth is 21.8 per cent with falling rents and sliding building values.

New research shows Perth businesses are swapping suburban office space for the CBD - and many the new arrivals have nothing to do with mining. Credit:Philip Gostelow

Perth is leading the nation in office vacancy rates and the Property Council's half-yearly Office Market report, to be released on Thursday morning, shows vastly different scenarios for Australia's top office precincts, led by supply and demand and driven by the cities' economies.

Sydney and Melbourne have the strongest numbers, with Sydney facing some new supply and Melbourne challenged by a surprising weakness in demand. In Brisbane the demand has been surprisingly strong but the challenge is new space coming on-line.