Mahesh Jethmalani's decision came nearly a fortnight after his father and BJP's Rajya Sabha MP Ram Jethmalani asked Gadkari to quit the post and not to seek a second term in office in the wake of allegations against him.
"I do not deem it morally and intellectually appropriate to continue to serve on the party's national executive as long as you are the president," Jethmalani said in a brief, single sentence letter to Gadkari.
Gadkari is in the line of Opposition fire following media reports about dubious funding of his company Purti Sugar and Power.
Ram Jethmalani had also attacked Gadkari about a fortnight ago, saying he should quit in the interest of the party and his own.
"In the interest of the party, in his own interest, he should get out of the fray now and he must give the position to somebody who inspires greater confidence. He should not aspire for a second term," Ram Jethmalani had said.
Maintaining that Gadkari's continuance weakened the party's position, Jethmalani said, "Obviously, there is suspicion about his integrity and in the interest of the party and his own interest he must get out of this position.
"It weakens the party position. In the coming elections we are fighting against corruption and we have to have a man of absolute impeccable integrity," he had said.