Nasdaq, the US electronic stock market, has cast doubts on the future of a 27-year-old US exchanges' trading network after announcing its decision to withdraw from the group last week.

Chris Concannon, vice-president of transaction services division at Nasdaq, said: "When I look at technology, there is no long-term future for the Intermarket Trading System. There will come a point with the increase in trading activity where there are capacity issues on the system."