The banking regulator yesterday warned big lenders of the risks of lending to real estate developers and highly polluting or energy-intensive firms, ordering them to step up controls to prevent a rebound in bad loans.

Despite a drop in their non-performing loan ratio in 2007, banks should not be complacent because they face stiff challenges ahead, Jiang Dingzhi, vice-chairman of the the China Banking Regulatory Commission, told executives from the big lenders.

"Banks should carefully implement the government's macro control policies and effectively prevent various dangers," he said.