Instinet, an electronic share-trading platform, has asked the US Securities and Exchange Commission to rethink plans for a strict trade-through rule, which aims to guarantee best-price execution across exchanges.

In a letter to the regulator, Edward Nicoll, chief executive of the platform, said: "Instinet does not believe that a strict trade-through rule, such as that proposed by the commission, is in the best interests of investor or the markets."