The WBO heavyweight champion held a press conference last week to issue a challenge to his British rival and his promotional team Duco Events have since suggested they will accept a 60-40 split in favour of Joshua, the reigning WBA 'super' and IBF title holder.
But David Higgins, a director at Duco Events, is prepared to abandon negotiations following an opening email from Joshua's promoter Hearn.
"I got this weird email from Eddie's email address, but he must have been hacked," Higgins told Sky Sports. "He made the most ridiculously low offer. It could have been the most insulting offer in boxing history.
"To expect 40 per cent is actually quite reasonable, because you have earned it, and it's a unification.
"Of course I have mentioned it [to Joseph Parker] and he just laughed like I did.
"I'm not going to reply, because I don't think it was Eddie Hearn. I reckon someone hacked his account, it was a scam. I reckon Eddie respects boxing and I reckon Anthony Joshua wouldn't want to insult Joseph Parker.
"Joseph has worked his way from the ground up and earned the right. Joshua, I think, would understand and respect that, so it can't possibly be AJ or Eddie that made the offer. It must be an email hack."
Hearn has also been holding talks in America about another potential unification with WBC champion Deontay Wilder and Higgins is willing to consider other options, including a trans-Tasman fight with Lucas Browne or another bout in China.
"I'll give you a simple answer. They pay us 40 per cent and not a cent less, or they will fight Wilder, who will obviously win and then we'll fight Wilder 50-50," said Higgins. "If they want to go fight Wilder they can - and then we'll fight Wilder on a 50-50 basis later in the year, once he has all three belts.
"We will come to England and fight AJ, but 40 per cent is the bottom line and I can give my word now, not one per cent less.
"We have got several fights on the table and I tell you this, we have pretty much given up on Joshua. Assuming someone hacked his email, I apologise to Eddie and he's welcome to give me a call. He's got my number if he wants to actually make a respectable offer.
"Joseph has earned the right. He's going to put it all on the line and deserves a fair payday. The terms they offered disrespect every kid in the world who wants to become heavyweight world champion and set their family up for life."
If Joshua does fight Parker, Sky Bet have him as their 1/25 favourite with the New Zealander 8/1 and the draw 33s.
