Venezuela's opposition has presented to the electoral authorities a petition with the signatures of 1.85 million voters calling for a referendum to oust President Nicolas Maduro.

This is the first step in a process which could lead to a recall referendum being held by the end of the year.

The opposition blames the socialist government's policies for the current economic crisis and the shortage of staple goods in many shops.

Mr Maduro's term ends in 2019.

The executive secretary of opposition party MUD (Democratic Unity Roundtable), Jesus Torrealba, said he had handed over to the National Electoral Board 80 boxes with the signed papers.

"With this successful strategy, MUD moves forward in its bid to achieve urgent political change through strictly peaceful and constitutional means," Mr Torrealba said.

Speed up the process

Under Venezuela's constitution, presidents can be removed from office by means of a referendum once they have served half their term.

Mr Maduro took office in April 2013. He was elected to replace Hugo Chavez, who died of cancer.

At this earliest stage, 1% of those on the electoral roll must sign the petition to start the process.

The opposition needed to collect about 200,000 signatures in up to 30 days.

But almost 10% of the electorate signed this first petition in less than a week, said Mr Torrealba.

The electoral authorities said the opposition might have to wait for the end of the 30-day deadline to begin gathering signatures for a second petition.

The opposition disagrees. The MUD wants to speed up the process in order to try to hold a referendum by December.