The landmark merger that created Citigroup was a “mistake” that failed to benefit the financial services conglomerate’s investors, customers and employees, says John Reed, who masterminded the $166bn deal with Sandy Weill in 1998.

Mr Reed’s comments come days before Sunday’s 10th anniversary of the merger announcement and underline the challenges faced by Vikram Pandit, who took over as Citigroup chief executive in December, as he tries to revive the company.