France is planning to clamp down on the publication of exit polls and election results ahead of their official release, especially on social media, the poll watchdog said on Wednesday, four days before the first round of the presidential election.

French law forbids pollsters from releasing vote estimates on election day and the day before, but the emergence of technology such has Twitter has made it more difficult to control potential leaks of voting trends.

The Poll Commission, which regulates pollsters, is due to outline on Friday the measures it will take to prevent leaks on sites such as Twitter and Facebook as well as traditional media after newspaper Liberation hinted it might break the embargo.

The aim is to protect the last voter to vote, a commission member told Reuters, without specifying what the measures would be.

However, there is little the commission can do to prevent people from consulting the websites of media in Belgium and Switzerland which routinely report exit polls in French election in the hours before results are officially published from 8 p.m. (1800 GMT). Polls close at 6 p.m. though in big cities it is 8 p.m.

During the first round of France's 2007 election, the websites of several Swiss and Belgian newspapers crashed under the weight of French web surfers trying to consult them, prompting some to boost their capacity before the 2012 election.

Some opinion polls show incumbent President Nicolas Sarkozy slightly ahead of Socialist challenger Francois Hollande in Sunday's first round of voting. However, Hollande has a wide lead of about 10 percentage points for a May 6 runoff.