There is probably never a good time to be hauled before a court by a corporate regulator, but for Citigroup Inc.’s Australian subsidiary, this is certainly not one of them.

The Australian Securities & Investments Commission last month launched a civil suit against the world’s biggest bank, alleging it failed to properly manage a conflict of interest when one of its principal traders in Sydney, Andrew Manchee, bought shares in Patrick Corp. Ltd. last August, just as the bank’s investment banking division was preparing a bid on behalf of client Toll Holdings Ltd. ASIC has thrown an insider-trading charge against the bank as well.