Russian conglomerate Interros has infuriated the banks leading the $2bn (€1.6bn) initial public offering of Rosbank, a subsidiary, after last night agreeing to sell 10% of the firm to Société Générale without telling them.

The agreement, which came less than 12 hours before bankers were set to launch the flotation, will see Société Générale buy 10% in Rosbank for $317m.