Protesters hold a France's national flag (R) and a red flag, on May 5, 2013 on the Bastille square in Paris
Tens of thousands of protesters took to the streets of Paris on Sunday to mark Socialist President Francois Hollande's first year in office by accusing him of turning his back on the left.
On the eve of the anniversary of his May 6 win last year over right-winger Nicolas Sarkozy, the Communist-backed Left Front gathered supporters for the march from the Bastille, the iconic square of the French Revolution.
Thousands also gathered meanwhile for separate protests in Paris and other cities to oppose the government's plans to legalise same-sex marriage and adoption by gay couples.
The demonstrations come with polls showing Hollande as the most unpopular president in modern French history. Many voters are angered by an economy on the edge of recession and unemployment hitting a 16-year high.
Jean-Luc Melenchon, the Left Front's firebrand candidate in last year's presidential vote, called the protest in Paris last month at the height of a scandal over Hollande's ex-budget minister Jerome Cahuzac being charged with tax fraud.
Melenchon told the crowd -- estimated by organisers at 180,000 but by police at 30,000 -- that the Socialist government had betrayed its supporters on the left.
"We do not want the world of finance in power! We do not accept the politics of austerity!" he told protesters waving the red flags of left-wing movements.
In an interview Sunday with newspaper Le Parisien, Melenchon called on Hollande to "return to the left, where he was when he was elected".
He accused Hollande of contributing to Europe's economic crisis by focusing on "the interests of shareholders, of big business and of European austerity policies, to the detriment of the workers."
Melenchon called for a government reshuffle with himself or Industrial Renewal Minister Arnaud Montebourg -- considered one of Hollande's most left-wing ministers -- as prime minister.
Opponents of gay marriage meanwhile rallied in major cities in a bid to force Hollande to back down from signing a bill approved in parliament last month.
The bill, which is also facing a constitutional challenge, sparked months of demonstrations across the country, with some descending into violence.
It has been one of the most controversial reforms of Hollande's first year in office, with right-wing opponents demanding the issue be put to a referendum.
Thousand of protesters rallied in cities including Paris, Lyon, Rennes, Lille and Montpellier to demand the bill be struck down.
In Paris, where police said about 15,000 took part in a rally, organisers said it was still possible for the bill to be defeated.
"There have been several cases in recent history of laws that were approved and then withdrawn. We are not without hope, on the contrary, we think that Mr. Hollande will in the end listen to the French people," said Ludovine de la Rochere, the head of the "Manif Pour Tous" (Protest for All) group that has organised demonstrations.
Sunday's protests follow another demonstration on Wednesday that brought hundreds of supporters of the far-right National Front to the streets of Paris, as a poll showed its leader Marine Le Pen would come second to Sarkozy if an election were held now, far ahead of Hollande in third place.
Since his election, Hollande's approval rating has fallen faster and further than any other president's since the founding of France's Fifth Republic in 1958.
The government has said it will hold a meeting on Monday to set its agenda for the months to come, with the focus on tackling unemployment, boosting economic growth and controlling public finances.