Parker and Whyte agreed a belated deal to meet on July 28 at The O2 Arena after the latter pulled out of two world title eliminators.
The winner could move closer to a rematch with Anthony Joshua and BetStars are struggling to split the pair ahead of the PPV battle.
BetStars Director of Trading Ian Marmion said: “Dillian Whyte will take on Joseph Parker in a heavyweight showdown at the O2 on July 28 as both fighters look to force themselves into world title contention. It promises to be a blockbuster bout between two fighters whose only blemish on their record is a defeat at the hands of Anthony Joshua.
“Whyte edged himself closer to a shot at the world title after knocking out Lucas Browne back in March to extend his record to 23-1. However, ‘The Body Snatcher’ is the slight underdog at evens to claim the bragging rights in this high-stakes clash next month.
“For Joseph Parker, this clash will be his second consecutive fight on UK soil. The New Zealander lost his WBO belt to Anthony Joshua at the Principality Stadium back in March and is the only man ever to take AJ the full distance.
“The former WBO world heavyweight titleholder will fancy his chances in this one and Parker is the early odds-on favourite at 4/5 to come out on top against the Brit . Meanwhile, both fighters to share the spoils on the night can be backed at 25/1.”
Whyte v Parker, odds from BetStars
Joseph Parker to win – 4/5
Dillian Whyte to win – Evens
Draw – 25/1