"These accusations are based in anger and are false - to the extent that she claimed my father is the richest man in Malaysia," he said.
Mahmud was testifying in the trial over a RM100mil mutaah (conciliatory gift) divorce settlement claim filed by his ex-wife Shahnaz A. Majid, 51.
He added that he did not understand Shahnaz's claim for "hundreds of millions of Ringgit".
Mahmud also disputed Shahnaz's claim that he was involved in businesses worth billions of Ringgit, and was the executive chairman of Cahya Mata Sarawak, when he was actually its deputy chairman.
"She said we have oil palm on our land which was generating revenue. We have bushes and shrubs on it and if you want to value them as oil palm ... then she is lying," said Mahmud, referring to a plot of land he owned which was valued by Shahnaz's accountant.
He explained that the land received by his companies from the Sarawak government was payment-in-kind for government projects such as bridges.
"The state government did not have the money to pay me, so it was payment-in-kind," said Mahmud.
He also disputed Shahnaz's claim that he had assets worth billions of Ringgit as well as offshore bank accounts.
"There are no accounts in Switzerland, Luxembourg, Hong Kong and the Caribbean. What was supposed to be a private matter in divorce maintenance claims has been turned into an attack to change the political landscape of Sarawak," said Mahmud.
Mahmud accused several parties - including his wife, her legal team and Opposition leader Datuk Seri Anwar Ibrahim - of working together to tarnish the name of his father and his family.
"This Court has become a means for Opposition politicians to tarnish me and my family's name, and for NGOs to tarnish Sarawak's name with false allegations. They wish to say my father is corrupt, when he has served his country and his state with honesty," said Mahmud.
Earlier, Mahmud denied punching and strangling Shahnaz.
He, however, admitted to pushing Shahnaz once when she tried to scratch his face.
"There was an incident where she wanted to scratch my face, but I pushed her hand away and she fell to the floor.
"She was not injured when she fell as she landed on a carpet and did not hit any chairs, walls or the floor," said Mahmud.
Mahmud added Shahnaz had displayed violent behaviour towards him on more than one occasion.
"She tried to scratch my face as she thought I was cheating on her. When she said I hit her, she lied. There is no proof and there are no witnesses," he said.
The hearing continues before Syarie judge Muhamad Abdul Karim Wahab on Sept 9.