Henrique Capriles told the BBC that 80% of the population wanted change and he would be able to collect 4m signatures and force a recall referendum.
"We are having the worst situation in our history," he said.
Oil accounts for most of Venezuela's export revenues but plummeting prices and economic mismanagement have brought the country to economic collapse.
Last month pro- and anti-government demonstrations attracted hundreds of thousands of people.
Jobless and bereft in industrial city of Valencia
Going hungry in Venezuela
What has gone wrong in Venezuela?
Opposition supporters blame Mr Maduro for Venezuela's economic crisis and accuse the electoral commission of delaying a referendum that could shorten his stay in power.
But Mr Capriles said he believed he could force a referendum to take place.
"We have to collect signatures," he said.
"It's four million people and that is going to be so important that it is going to open the door for the referendum and the people are going to vote and we are going to have a new government in our country.
"It looks very difficult to have it, but so important that it is going to be very difficult for Maduro to avoid the referendum."
Mr Maduro accuses the opposition of trying to stage a coup.
Venezuela's opposition leader says he is confident he will be able to force President Nicolas Maduro to step down.