Deutsche Börse, the operator of the German stock exchange, is drawing criticism for not subjecting its new trading platform, Xetra Best, to sufficiently rigourous testing.

Critics claim that the system's test, which starts Monday, leaves out important Dax and M-Dax stocks - 20 are included in the simulation, although they are not specified publicly. The new system will allow banks and brokerages to execute trades for private investors directly, saving on broking and dealing costs. The system itself is not without its critics, however, who fear it will reduce liquidity and increase spreads for investors.