Mr Obeid, 72, was flanked by his legal team as he arrived for the first day of his criminal trial at the historic Darlinghurst Courthouse on Wednesday.

"Not guilty, Your Honour," he said from the mahogany dock.

Mr Obeid is charged with one count of misconduct in public office over representations he allegedly made to Steve Dunn, then deputy chief executive of the state Maritime Authority, about the grievances of a group of Circular Quay retailers in 2007.

The retailers were seeking to renew their leases without competing in a public tender process.

In his opening address to the jury, Crown prosecutor Peter Neil, SC, alleged that Mr Obeid "acted in wilful and serious breach" of his obligation to act "solely in the interests of the public" by failing to disclose to Mr Dunn that his family had a financial stake in two cafes on the wharves at Circular Quay, Cafe Sorrentino and Quay Eatery.

The retail leases for the cafes were acquired in 2002 through a private company, Circular Quay Restaurants Pty Limited.

The court heard that cash receipts from the two cafes were "regularly collected and out of those cash receipts payments were regularly made" to members of the Obeid family, "principally Mrs [Judith] Obeid, the accused's wife".

He said the cash - about $1000 a week - was used for housekeeping.

Mr Neil said that Mr Obeid, then a member of the NSW upper house, had previously been Fisheries Minister when Mr Dunn was a director and later director-general of the Fisheries Department.

Mr Dunn "came to regard Mr Obeid as a close professional colleague and friend" for whom he had "considerable respect", Mr Neil said.

Mr Obeid "represented that he was acting on behalf of constituents" when lobbying Mr Dunn on behalf of the retail leaseholders when "in fact he was acting in the private interests of himself and his family".

Mr Neil said Mr Obeid must have known Mr Dunn "had a high regard for him" and was "brand new" to the Maritime Authority with "no background" in the retail leasing policies.

Mr Neil said Mr Obeid had a duty "to act in the public interest and only in the public interest" and "there must be no conflict between the financial or private interests...of a member of the legislative council...and the duty of a member to apply himself or herself solely to the benefit of the public".

He said the alleged wrongdoing "strikes at the heart of the duties" of members of Parliament and should attract criminal punishment.

The Crown is expected to call members of the Obeid family as witnesses, including Judith Obeid and the couple's eldest son Damian.

Former Labor Ports minister Joe Tripodi is also expected to give evidence.

The trial before Supreme Court Justice Robert Beech-Jones is slated to run for four weeks.