Responding to Sarkozy's alleged bias in favour of the rich, Villepin called for an end to the cap on taxes, introduced after Sarkozy's election as president, and called for greater redistribution of wealth.
Villepin stressed that his yet-to-be-named political movement, which will be formally launched on 19 June, would be “free and open to everyone”.
He told a press conference on Thursday that he felt uncomfortable with the political policies that are currently being pushed by the majority.
“My campaign slogan is a republic of solidarity,” he said, admitting he is still a member of France’s ruling UMP party.
Villepin, who was in January cleared of a smear campaign against Sarkozy, also said he wanted to stop political interference in judicail affairs.
Both he and Sarkozy had served as ministers under former president Jacques Chirac, but fell out over who should succeed him.
After its defeat at last weekend’s regional elections, the UMP is increasingly divided over Sarkozy's leadership.