Henrique Capriles has asked for a recount after his defeat in the recent Venezuelan presidential elections.
The grandson of Jewish immigrants, Mr Capriles lost to his rival Nicolas Maduro by 1.6 per cent when the results were announced on Sunday.
According to sources, Mr Capriles said that he would not consider the government legitimate without a recount and called on his supporters to protest in the streets.
Mr Capriles said: "If both parties said that they agreed to count all votes, why the hurry? What are they hiding?"
"I want the clanging of pots and pans to be heard around the world. We must let the world know our rage and our indignation."
Accusations of election fraud have sparked protests in at least six cities across Venezuela. Reportedly, thousands of supporters of the opposition took to the streets in Caracas on Monday.
The Venezuelan electoral council has refused a recount. The inauguration of Mr Maduro is expected to take place on April 19.