Euronext, the pan-European stock exchange, is to press ahead with its float plans without including the Lisbon Stock Exchange, its new merger partner, in its valuation.

Euronext, which is hoping to be worth around €3.5bn ($3bn) when it lists on its own exchange next month, signed an agreement to merge with the Lisbon Stock Exchange on Wednesday evening. The two exchanges have been in formal negotiations since November last year.