He said the three were sitting on the grass when Clement grabbed one of the women from behind and held a knife to her throat.
He ordered the other woman to take off her clothes before robbing them of their money and fleeing into the night.
Mr Whittington said that as Clement left the park, he yelled: "If you follow me - you'll be dead".
But Clement made a "major hiccup" and left his wallet - including his driver's licence - at the scene.
Police took little time to track him down.
Mr Whittington said Clement had a while to make up a story and told the officers the women had robbed him in Albert Park before roughing each other up and running to the police.
He said there were two stories in the case.
"One is the truth - that's the girls'. The other is Clement's which the Crown says is a pack of lies."
Clement's lawyer Quintin Duff told the court that his client had been robbed at knifepoint and lost $700 before running off as fast as his "jellymeat legs" could carry him.
"You may be tempted to fall into the trap that the person who told the story first is telling the truth - the tell-tale is telling the truth."
But Mr Duff said his client did not go to police because every time he had talked to police it "goes badly".
"You're going to see that those words were oh so prophetic."
One of the women has returned to New Zealand to give evidence, the second will give evidence via audiovisual link from Germany.
The trial is set down for four days.
APNZ eg lb