PARIS, March 31 (Reuters) - French Interior Minister Manuel Valls, appointed prime minister by President Francois Hollande on Monday, is a centrist with a tough stance on law and order that is popular with the public but controversial in his own Socialist party.
The photogenic 51-year-old, naturalised son of a Spanish immigrant, is one the youngest ministers in Hollande's cabinet and an expert in political communication. He will need those skills to sell the president's U-turn to more business-friendly policies and impose discipline in place of cacophony.
His consistently high approval ratings as the nation's tough-talking "top cop" have contrasted with the record low poll ratings suffered by the president.
Some who know Valls say he harbours presidential ambitions of his own but that did not deter Hollande from picking him.
His past criticism of Socialist sacred cows such as the 35-hour work week introduced more than a decade ago, have earned him mistrust among party allies and comparisons with Britain's business-friendly "New Labour" ex-Prime Minister Tony Blair.
He supported shifting part of France's high tax burden from labour charges to consumption taxes, a policy proposed by former conservative President Nicolas Sarkozy and opposed by the Socialists.
Valls' support for the "No" camp which defeated a planned European constitution in a 2005 referendum brought him up against Hollande, a fervent "Yes" campaigner. But he went on to play a key role in Hollande's presidential campaign team.
A survey by the Ifop pollster in late February showed 49 percent of voters saw Valls as the most credible choice to replace Prime Minister Jean-Marc Ayrault, who resigned earlier after the Socialists were routed in local elections on Sunday.
Born in Barcelona, Valls took French citizenship in 1982 at the age of 19. He is regularly picked as the most popular French politician in opinion polls.
Hollande hopes the straight-talking appeal of Valls, a father of four whose second wife is a violinist, will help make key tenets of his supply-side economic policies more palatable to mainstream Socialist voters.
At the same time, Valls' reputation as a "Blairist" and a Socialist outlier may allay concerns among employers, who have been promised lower labour charges under Hollande's so-called "responsibility pact" in exchange for creating more jobs.
Long-time mayor of Evry, a gritty southern suburb of Paris, Valls' relationship with Hollande was not always rosy.
After their 2005 clash over the European constitution, Valls ran against Hollande in the Socialist primary in 2011 as a maverick who challenged the party to change its name and shed "outdated" policies, but received only 6 percent of the vote.
But after Hollande's victory in the primary, he was one of the first to back his former rival, becoming his communications director and a staunch ally in the battle to oust Sarkozy.
Earlier in his career, from 1997 to 2001, Valls served as communications director to Socialist Prime Minister Lionel Jospin under President Jacques Chirac.
According to Jacques Hennen and Gilles Verdez, authors of "Manuel Valls, Secrets of a Destiny", the media-savvy politician has long harboured presidential ambitions.
But he has not been without controversy.
Sometimes compared to Sarkozy for his tough talk and action-man demeanour, Valls has long had to fight off accusations from some on the Left and in the opposition that he is right-wing and would be better aligned with the conservative UMP party.
A supporter of the ban on full-face veils in public - a polarizing issue for France's Muslim population, the largest in Europe - Valls has taken a hard line on law and order issues, whether terrorism or petty crime.
He sent riot police to the southern port city of Marseille to control gang violence, expelled radical imams who preach hate from France, and staunchly defended police officers struggling to control youth violence in heavily immigrant suburbs.
While distancing himself from the policies of Sarkozy, who also earned his spurs as interior minister, Valls has continued unapologetically his practice of evicting Roma migrants from illegal makeshift camps and his crackdown on youth delinquency.
In recent weeks, Valls' approval ratings have fallen slightly following his role in banning a comedian deemed anti-Semitic from performing. Critics said Valls had gone too far and endangered free speech but the courts upheld his policy and the comedian, Dieudonne M'bala M'bala, dropped the offending show. (Reporting By Alexandria Sage; Editing by Paul Taylor)