The office vacancy rate in Perth's central business district is projected to rise to 12 per cent in two years, and climb even higher under a worst case scenario, while tenants are expected to have more bargaining power, an economic forecaster says.

The office vacancy rate in Perth's central business district is projected to rise to 12 per cent in two years, and climb even higher under a worst case scenario, while tenants are expected to have more bargaining power, an economic forecaster says.