ABP, one of the world's largest pension funds, is suing Citigroup as part of its $100m (€79m) claim against Qwest Communications International, the US telecoms group.

The defendants include Qwest directors as well as the group's auditors, Mark Iwan and Andrew Matasayama of Arthur Andersen; and Jack Grubman, the disgraced former telecoms analyst of Salomon Smith Barney (SSB), part of Citigroup.