In the early hours of yesterday morning, the Germans released further details of their offer that appeared to trump the proposal made by the New York Stock Exchange a day earlier.
A statement by Deutsche Börse asserted its offer valued Euronext shares at €76.60 (£52.28), €1.60 more than NYSE's bid. Euronext shareholders would be given 0.68 shares in a combined company, plus €7.72 cash, the Germans said.
The owner of the Frankfurt stock exchange and Eurex, the world's most lucrative derivatives platform, implied their proposed "merger of equals" would value the operator of the Paris, Brussels, Lisbon and Amsterdam exchanges and London's Liffe derivatives exchange at €8.6bn (£5.8bn), against €8bn under the NYSE's cash and paper offer.
However, to arrive at this more generous figure Deutsche Börse based its calculation on the closing prices of its own and Euronext shares on Monday, rather than the average price over three months that would be used should the pair combine, as is required under German law.
The share prices of Deutsche Börse and Euronext were significantly closer on Monday night than they have been on average over the past three months and, under the terms of the deal, that would be better for Euronext shareholders.
Serge Harry, Euronext's finance director, said: "This is the same offer that we received over the weekend and which was fully considered by the board. The figures as presented by Deutsche Börse are based on the closing prices on Monday, which is misleading because the proposal is based on the three-month volume-weighted moving average prior to the signing of the business combination agreement."
One sector analyst calculated that using the same model as Deutsche Börse's proposal, its offer fell to just €58 per Euronext share.
A Deutsche Börse spokesman said the statement was intended to flesh out details of the proposal already submitted to Euronext and the calculation had only intended to "illustrate the mechanics of our approach".
After a half-hour delay following Deutsche Börse's overnight statement, Euronext shareholders yesterday voted down a proposal to agree in principle to a merger of the two.
In Amsterdam, some 43,865 shareholders gave the thumbs down to the motion forced on to the agenda of Euronext's annual meeting by Winchfield Holdings, an investor with links to hedge funds, against 30,598 who backed the proposal.
TCI, a London-based hedge fund that holds about 10 per cent of Euronext shares, voted for a tie-up with Deutsche Börse.
Some Euronext shareholders at the meeting felt both offers undervalued the company. One said: "Let's not rush into anything, let's wait for a knockout bid. We have time to wait." Another said: "NYSE is trying to buy Euronext on the cheap and we are disappointed to hear management say that it is its preferred scenario."
Euronext's board, led by the chief executive Jean-Francois Theodore, laid competing merger proposals from Deutsche Börse and the New York Stock Exchange before shareholders.
Mr Theodore is thought to strongly favour New York but made no recommendation to shareholders at the meeting.
He and advisers at the investment banks Morgan Stanley and ABN Amro will continue to weigh up the merits of each proposal before making any recommendation to shareholders.
Deutsche Börse holds its own annual meeting for shareholders today. Reto Francioni, its chief executive, said: "We continue to believe in the strong substance and value, as well as the earnings accretion, of a combination of Deutsche Börse and Euronext to both shareholder groups under our proposal."
Over the next few days, Mr Francioni and his board will discuss yesterday's rejection by Euronext shareholders of the motion that asked of them whether a deal with the German exchange would be in the "best interests of all shareholders of Euronext".