Liffe, the London International Financial Futures and Options Exchange, has raised the stakes for its three potential bidders by telling them that it will not be interested in any bids that value it at less than £16 (€25.6) a share.

This is the &quotfair value&quot price that Liffe's shareholders agreed at this week's board meeting was the minium price at which they will be willing to sell out to any interested party. A minium price of about £16 a share values the futures market at more than £500m. The price takes into account the 5.06 million shares that would be created if Liffe's two biggest shareholders, Battery Ventures and Blackstone Group, were to exercise warrants on shares at £12 each.