The Premier League side were selected as the preferred option to take up residency at the site last December, but Hearn believes he can force a change to that decision.
The 65-year-old also questioned whether West Ham should be allowed to move away from their current home Upton Park.
"This is not a done deal," he said. "West Ham have an agreement but I have a judicial review outstanding and litigation with the Premier League that West Ham even moving would be a breach of Premier League rules.
"We have ended up in situation where we have gifted £500million of tax-payers' money to a Premier League club that has a turnover of more than £100m.
"This is state sponsorship beyond my wildest dreams. In effect it's rent free as they have ability to develop Upton Park."
However, West Ham vice-chairman Karren Brady denied claims that the stadium was a gift to the club and insisted they had agreed repayment plans.
"West Ham is not getting a free stadium," she declared. "The stadium was built for the Olympics and what are we going to do with it?
"Across the world stadiums that are not used die. Without anchor tenants the cost would be huge to the tax-payer.
"We hope the money generated from the sale of Upton Park will be enough to fulfil our commitment and to help pay off some of our bank debt.
"We have to pay off all our bank debt to move, we can't take the debt with us.
"If there is any excess from the sale it will meet some of that debt but I don't expect there will be."
