The Children's Investment Fund Management, the activist UK investor leading calls for a breakup of ABN Amro, has urged the Dutch bank to leave the door open for rival bids despite entering into exclusive talks with Barclays, the UK's third-largest bank.

TCI, which has a more than 1% stake in ABN Amro, sparked the debate over the Dutch bank's future a month ago when it urged other shareholders to vote against further acquisitions by the bank and instead pursue a sale or demerger. Shares in the Dutch bank have since risen by more than 19%.