PARIS (Reuters) - France plans new measures to clamp down on media and social networks that publish exit polls and partial results of Sunday's presidential election ahead of their official release, and will not hesitate to sue lawbreakers, the country's poll watchdog said.

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 new steps to prevent leaks on sites such as Twitter and Facebook as well as traditional media after the Liberation newspaper hinted it might break the embargo.

The panel said the new measures were aimed at preventing late voters from being swayed by early news on the voting trend and said it would pursue media outlets in neighboring countries like Switzerland and Belgium that violate French law.

In previous years the commission has been able to do little to prevent people consulting the websites of media in Belgium and Switzerland, which routinely report exit polls before results are officially published from 8 p.m. (1800 GMT). Polls close at 6 p.m. nationally and 8 p.m. in big cities.

"If there is a broadcast in France, the origin of the broadcast doesn't matter, the law has been broken and we will alert the prosecutor," said Mattias Guyomar, the commission's general secretary.

"We will consider there to be broadcasting in France from the moment that the site is consulted from an IP address in France," he added.

Any site that shares a link on Twitter or Facebook will also be in violation of the law, the commission said.

Both companies declined to comment.

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.

President Nicolas Sarkozy's re-election hopes suffered a double setback four days from the first round of voting when a string of public defections compounded the impression that his tumble in opinion polls is pushing victory beyond reach. ID:nL6E8FI1NT]

Sarkozy moved briefly into the lead in polls for the first round on April 22 following his handling of a shooting drama in southwestern France in March, but he has slipped back again in more recent polls and the runoff gap has widened.