The Investment Management Association, the trade association for British fund managers, has written a letter to the chief executive of the London Stock Exchange airing its concerns about the possibility of US regulation coming to the UK in the event of a merger with Nasdaq.

The letter to Clara Furse is the IMA's reaction to the comments of Callum McCarthy, chairman of the UK watchdog the Financial Services Authority, one month ago that regulatory framework's would have to be integrated "over time" to ensure the full benefits of a trans-Atlantic merger.