The owner of the largest US stock exchange has issued a stern warning to the Securities and Exchange Commission, saying the agency could be sued if it approves a competitor’s bid to become a fully-fledged stock exchange.

Nasdaq's attorneys wrote that the SEC would violate its own rules by approving the IEX Group.'s exchange, which includes a speed bump that slows incoming orders by 350 microseconds. The lawyers argued that the speed bump would trample rules that require orders be available immediately to other traders.