The head of the Organization of American States (OAS), Luis Almagro, has accused the Venezuelan President Nicolas Maduro of being "a traitor".
In a series of Twitter posts addressed directly to Mr Maduro, Mr Almagro also called him a "petty dictator".
Mr Maduro accused the OAS chief earlier this week of being a CIA agent and a traitor himself.
The Venezuelan president has blamed his country's economic crisis on an axis of enemy forces co-ordinated from the US.
During a three-hour long news conference on Tuesday, Mr Maduro had justified his declaration of a state of emergency by saying Venezuela was under attack from imperialist forces led by the CIA.
He then told journalists: "Almagro, just give up. He has been a traitor for a long time... At some point I will tell his story, I know his secrets. The Americans, the CIA, have played a master move using Almagro as their agent."
Opposition politicians have handed in a petition with 1.85 million signatures to the electoral authorities requesting a referendum be held to recall Mr Maduro from office.
But Mr Maduro's deputy, Vice-President Aristobulo Isturiz, on Sunday ruled out such a referendum, saying the signatures were "fraudulent".
Mr Almagro said that not letting the referendum go ahead made Mr Maduro "another petty dictator".
While President Maduro did not answer Mr Almagro's tweets directly, Venezuelan Foreign Minister Delcy Rodriguez did.
She wrote, "Mr Almagro, every time you make a statement you express your hatred against Venezuela and its legitimate authorities. You are part of the imperialist detritus."
"You only repeat the scripted words which your imperialist masters dictate to you".
"You will never give orders to Venezuela!"