Janet Yellen warned US trading partners against currency manipulation and touted the importance of market-based exchange rates, in her most exhaustive comments yet on the incoming Biden administration’s approach to international economic policy.

Ms Yellen, who is Joe Biden’s nominee to serve as Treasury secretary, said “the intentional targeting of exchange rates to gain commercial advantage is unacceptable”, and she would “oppose any and all attempts by foreign countries to artificially manipulate currency values to gain an unfair advantage in trade”.

Ms Yellen, the former Federal Reserve chair, was speaking during a confirmation hearing before the Senate finance committee, where she is expected to receive broad backing to take the top cabinet job responsible for managing the US economy under Mr Biden.