Former French president Nicolas Sarkozy has revealed he will run again to be leader of his country in next year's elections.

The 61-year-old, who served as president between 2007 and 2012, was unseated from the Elysee Palace when he was defeated in the last French presidential election by Francois Hollande.

The Socialist leader has since proved increasingly unpopular as many of the reforms he has tried to institute have failed. 

Mr Sarkozy wrote on his social media pages, ahead of the publication of his book Everything For France: "I have decided to be a candidate for the 2017 presidential election.

"I felt I had the strength to lead this battle at a troubled time in our history."

He has been a member of France's right of centre Republicans party since 2015, having previously represented its predecessor Union for a Popular Movement.

It was not clear from his posting whether he will try to take part in the primaries to win the ticket to be The Republicans' candidate, or whether he will stand independently.

It is understood that up to a dozen other The Republicans politicians are vying to become their party's candidate, including Mr Sarkozy's main rival and former foreign minister Alain Juppe.

The ex-head of state, who became as well known internationally for his fashion sense and marriage to model Carla Bruni, was formally investigated by French authorities in 2014 on suspicion of so-called "influence peddling" and questioned at a Paris police station.

In 2013, he was also formally investigated over "abuse of frailty", in connection with an illegal party-financing case linked to France's richest woman, Liliane Bettencourt.