Commercial property continues to drag down the credit quality of bank profits. Bank of Queensland yesterday blamed this aspect of its lending for a projected doubling in bad debt expenses for the half year to February 2011.In a statement issued late yesterday, BOQ said it had revised its profit outlook for the year to August 2011 of between $210 million to $230 million, which is still an increase of at least seven per cent on 2010.BOQ said it had conducted "an extensive review of its commercial lending portfolio" and said it chose to do so "in response to weaker than expected trading conditions" in this portfolio.The bank said the review covered the top 250 commercial exposures. This included all commercial property exposures of more than $5 million and comprises seven per cent all lending and 35 per cent of commercial exposures by value.BOQ said it lifted its projected bad and doubtful debt expenses to between $85 million and $90 million for the first half of the year, "based, in part, on an increase in impaired commercial assets of $97 million".The bank provided one piece of data on its wider business, saying that lending in the two months to October 2010 was "growing above our guidance of 1.5 to two times system growth."