Mel Gibson I Didn't Agree To Pay Alexander $100K

9/27/2011 1:15 PM PDT

Mel Gibson -- I Didn't Agree to Pay Alexander $100,000

Mel Gibson is taking issue with legal documents filed by Oksana Grigorieva's lawyer -- which state that Mel paid $100,000 to Oksana's son Alexander Dalton, the son she had with actor Timothy Dalton.

Mel's rep tells us, "The deal between Mel and OG is exactly what was set forth on the record, in open court, on Augst 31, 2011" -- when Mel agreed to pay Oksana $250,000 as part of their custody settlement agreement.

His rep continues, "Mel is paying exactly the sums set forth to OG -- and is paying no additional sums to Alexander Dalton or anyone else."

"How OG chooses to have any sums due from Mel allocated is her business."

But as we previously reported, TMZ has obtained legal documents filed by Oksana's lawyer -- which claim, "Of the first $250,000 paid ... $100,000 belongs to Alexander Dalton who is waiving his rights to sue Mel Gibson and must be compensated for this to be lawful."

The docs continue, "If Alexander Dalton does not get his $100,000.00, he cannot waive his rights to sue. Mr. Gibson negotiated for that as a part of the settlement and is entitled to the benefit of his bargain."