O'Riley rejected a claim by the Ratepayers' Alliance the pair had no responsibility for major events or working in the department responsible for attracting commercial investment to Auckland.
"The Ratepayers Alliance have completely missed that Steve Armitage has much wider responsibilities within Ateed, including general management responsibility for our tourism and international education activities, World Masters Games, and the NZOC partnership.
"Susan has managed our local and international sporting federation relationships for several years. The NZ Inc programme of activity they are supporting in Rio reflects all of those priorities and several others, and is tied to measurable outcomes within our business plan," O'Riley said.
He said Ateed was part of the NZ Inc. Programme of activities that are happening this week in Brazil, with staff taking part in meetings that span a range of opportunities for Auckland.
"This includes promoting World Masters Games 2017 (being held in Auckland), meeting with international sporting federations to prospect for future major events opportunities for Auckland, progressing a bid for the IOC Congress 2021, tourism, international education and trade opportunities.
"Our representatives have also met with investors who have an existing relationship or wish to build a relationship with Auckland as a place to invest."
Alliance spokeswoman Jo Holmes said: "While you could understand a member of the Auckland World Masters Games organising team attending Rio, the two staff Ateed have sent have nothing to do with organising events. It's a junket on our dime, plain and simple.
"If Ateed was at the Olympics to attract events or competitions to Auckland, they would have sent someone from their events department. Likewise, if they were there to promote Auckland investment, they would have sent someone who works in that area."
Six days ago, the Herald revealed that Alf Filipaina, the councillor leading the council's planning blueprint, was in Rio while his colleagues ploughed through the details and final decisions in Auckland.
He took leave from his $105,800-a-year role to attend the Olympics, even though he was chairman of the Unitary Plan committee, which oversaw the council's position on the blueprint, or Unitary Plan.