Shareholders who lost millions investing in Eddie Obeid-linked company Australian Water Holdings are suing its former chairmen, federal Assistant Treasurer Arthur Sinodinos, former NSW treasurer Michael Costa and Liberal fundraiser Nick Di Girolamo for misleading and deceptive conduct.

Mr Di Girolamo's brother-in-law, his best friend from school and the well-connected Navarra family, who run reception centres including Le Montage, Curzon Hall and Conca D'Oro, are alleging Mr Di Girolamo used emotional ''manipulation and control'' to get them to invest in the infrastructure company.

ICAC continues to investigate whether Eddie Obeid (pictured), Mr Tripodi and Tony Kelly used their positions as MPs to benefit the Obeid-linked company, Australian Water Holdings. Credit:Peter Rae

Also involved in the Federal Court suit are Anthony Karam and his sister Corienne, who are tenants of the Obeid family in a restaurant in Broadway.

Mr Di Girolamo, a prominent Liberal Party fundraiser and associate of the Obeids, is one of those to be examined at an ICAC investigation into Australian Water Holdings. The inquiry will commence on Monday.