French presidential election frontrunner Francois Hollande said on Thursday he would order an audit of public finances if elected in May, a day after setting an ambitious timetable for implementing his tax-and-spend promises.

The Socialist candidate, leading conservative President Nicolas Sarkozy in polls for a May 6 run-off, made the announcement hours before his rival was to present a costed manifesto in his uphill battle for re-election.

We'll have the Court of Auditors carry out an evaluation immediately ... and freeze certain spending once we have the results, Hollande said in an interview on Canal+ television.

The move appeared designed both to steal some of Sarkozy's thunder and to prepare the ground for austerity measures that could be blamed on his predecessor's handling of France's debt and deficit.

It also came after a cover story in the Economist weekly entitled France in Denial made waves in political circles by accusing both leading candidates of lacking serious ideas for tackling the country's economic and fiscal problems.

Hollande and his allies derided Sarkozy for waiting until less than three weeks from the first round of voting on April 22 to produce a comprehensive manifesto.

It's not very serious, said Socialist Party chief Martine Aubry, who made a point of noting that Hollande had presented a fully costed manifesto in January.

Sarkozy's programme is his record of the past five years, only worse, said Hollande, whose main line of attack is that the wealthy rather than the needy were the big beneficiaries of tax giveaways since 2007.

The Socialist candidate, who proposes hiring 60,000 school staff and creating 150,000 state-aided jobs if he wins power, said he hoped to ensure recruitment of 4,000 school support staff before next September's start of a new academic year.

He also announced plans to freeze fuel prices for three months, increase a back-to-school bonus for poorer families by 25 percent and slap a 75-percent top income tax rate on people earning more than 1 million euros (825,000 pounds) a year.

Sarkozy was to unveil his manifesto on Thursday afternoon but was not expected to announce significant new proposals.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Election polls graphic http://r.reuters.com/was36s

Interactive timeline http://link.reuters.com/wun96s

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

LOSING MOMENTUM?

An opinion poll published on Thursday suggested the president may be losing momentum after recent poll gains.

The CSA poll showed Sarkozy's predicted first-round score stable at 30 percent, and Hollande's rising by three points to 29 percent from a survey a week earlier by the same institute.

It showed Hollande winning the runoff against Sarkozy with 54 percent support, one point higher than previously.

Sarkozy leads Hollande in most polls of first-round voting intentions but has been shown by all polls without exception to be the loser in the decisive round.

In a symbolic show of support for Hollande, his former partner Segolene Royal, who was the unsuccessful Socialist presidential candidate in 2007, joined him on stage as co-star at a rally in the city of Rennes on Wednesday night.

She and Hollande's current partner, journalist Valerie Trierweiler, shook hands in a display of conciliation.

The most noble way to make history is to back the person who's best placed to win, said Royal, who live with Hollande for a quarter of a century and had four children with him.

(Reporting By Brian Love; Editing by Paul Taylor)