THE $4 billion (£2.3 billion) merger of the New York Stock Exchange and Archipelago, an electronic share trading group, will be at the centre of fresh controversy this week as members of The Big Board demand the release of additional secret documents about the merger, amid growing threats of blocking the deal.

By the end of this week John Thain, the NYSE chief executive, will make public previously secret documents detailing private negotiations that led to the exchange agreeing the Archipelago merger. Yet Stock Exchange members want even more information than Mr Thain is prepared to reveal before they will consider giving the deal approval, The Times has learnt.

The dossier that Mr Thain has agreed to make public will include a document written by Lazard, the investment bank, to give an impartial view of the merger proposal. He agreed to reveal the dossier after a court order last week, which was made after members of the NYSE had sued the exchange for the right to review the documents before the proposed merger advanced any further.

Yet, according to a letter sent to all members of the NYSE, the members also want to see the source material that was used to write the fairness opinion, which will include a detailed account of the NYSE’s day-to-day business and other elements of the private company’s inner workings.

The members also want to see more detailed information about the valuation of the NYSE than Mr Thain is prepared to reveal. They are expected to file a legal action to try to force the NYSE to reveal the material they want.

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