Canberra's office vacancy rate has increased over the past six months, with one grade soaring to more than double its previous rate according the latest Office Market Report from the Property Council of Australia.

Canberra continues to have the highest office market vacancy rate of any capital city, rising to 11.9 per cent from 9.8 per cent in July, however industry representatives have attributed the jump to an increase in stock.

The vacancy rate for B Grade space increased from 5 per cent to 11.2 per cent over the six month period, while the rate for A Grade office space increased from 10.8 per cent to 11.8 per cent. The vacancy rate for C Grade space also increased, however D Grade rates decreased.

A significant amount of space is due to come online throughout the coming year, according to the Property Council. The 113,770sqm of stock, 75 per cent of which has been pre-committed, represents 5 per cent of the current market size.