The proposed $170bn merger between miners BHP Billiton and Rio Tinto would be “terrible” for global competition and should be rejected by anti-trust regulators, according to Zhang Xiaogang, China’s most powerful steel industry executive.

The comments by Mr Zhang, chairman of the China Iron and Steel Association and of Ansteel, one of the country’s biggest steelmakers, are among the harshest criticisms of the proposed deal.