French President Francois Hollande and his Prime Minister Manuel Valls are under open from the left flank of the governing Socialist party, with leading figures accusing the pair of crippling the country.

With 15 months to go until the presidential election at which Hollande is expected to seek a second term in power, Martine Aubry -- a powerful ex-minister and daughter of former European Commission chief Jacques Delors -- led the charge.

In a full-page editorial in Le Monde newspaper on Wednesday which was co-signed by 17 other left-wing figures including firebrand former MEP Daniel Cohn-Bendit, Aubry blew open the divisions between the left of the party and its reformist side, saying Hollande's policies were driving France towards "long-term weakening".

"Enough is enough," Aubry wrote, asking: "What will remain of the ideas of Socialism when, day after day, its principles and its basis are being undermined?"

Aubry, the mayor of the northern city of Lille, reserved particular vitriol for Emmanuel Macron, the reform-minded economy minister and former investment banker who is a frequent target for the Socialist Party's old guard.

"Emmanuel Macron? I have just had enough of him," she said in a later interview.

Aubry insisted however that she has no intention of running for president in 2017 -- she claimed her concern was the very future of the party.

Valls hit back on Thursday, saying Aubry had not set out "a single policy proposition" in the article.

"I am the head of the government, I don't write declamatory editorials," Valls told Le Monde.

- Choppy waters ahead -

But many commentators noted that Aubry's offensive was largely greeted by silence in official quarters. Valls waited 24 hours before responding while Hollande, who is visiting Latin America, has said nothing.

Newspaper editorials predicted that Hollande was about to enter choppy waters.

Some spoke of a "split" in the Socialist Party, others of a "dynamiting" of Hollande's proposals.

Frederic Dabi, from the Ifop polling institute, said he had never seen "such a strong protest from a faction of a majority party" with just one year to go to the presidential election.

The article comes as Labour Minister Myriam El Khomri is seeking to simplify France's complex labour laws, which some blame for fuelling stubbornly high levels of unemployment in the second-largest eurozone economy.

Most of the ministers who carry the torch for the left wing of the Socialist Party have left Valls' government, most recently justice minister Christiane Taubira, who quit over her opposition to the government's plans to strip terror convicts of their French nationality.

Hollande's government has been accused by the rebellious leftist flank of veering to the right with the introduction of harsh security measures after the jihadist attacks in Paris that left 130 dead in November.

And a series of economic reforms adopted last year as France seeks to revive its stagnant economy were slammed as overwhelmingly pro-business. Valls had to force the measures through parliament over fears those within the party would sink the bill.

Despite his poor record on reducing unemployment, Hollande is gunning to be the Socialist candidate for the presidential election.

Former president Nicolas Sarkozy and one-time prime minister Alain Juppe are among those vying for the right-wing nomination, but all the candidates fear a potentially high level of support for far-right leader Marine Le Pen.