It's time executives at the Nasdaq Stock Market ( NDAQ) and London Stock Exchange ( LSE.L) grow up.

Nasdaq's nearly yearlong campaign to acquire the London exchange has deteriorated into a cross-Atlantic food fight, with each side firing off angry missives. The managements of both exchanges have turned to childish banter as the deadline fast approaches for London shareholders to accept Nasdaq's $5.3 billion hostile bid.

Throughout the escalating war of words, Nasdaq has refused to budge from its 1,243-pence-per-share bid, a figure London officials repeatedly have said is too low to consider. Perhaps the defining event of this increasingly bizarre corporate takeover came on Tuesday when Chris Gibson-Smith, the chairman of the London bourse, told Nasdaq officials to "shut up or put up."

Nasdaq has done neither. On Wednesday, Nasdaq CEO Robert Greifeld told Reuters he sees little chance of the exchanges "getting together between now and Saturday." That's a reference to the deadline for London shareholders to accept the Nasdaq bid under British takeover law.

The long and acrimonious battle is quite a contrast to the orderly manner in which the New York Stock Exchange ( NYX) has pursued its friendly $14 billion merger with Paris-based Euronext, one of Europe's largest derivatives and stock exchanges. Even if Nasdaq can persuade enough London shareholders to accept the bid, its management has tarnished itself in the process.

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