Baroin tried to highlight the risks facing defectors by citing the example of Manuel Valls, a former Socialist prime minister who said he was ready to back Macron in the June election.
Macron's year-old Republic on the Move party does not have any seats in the current parliament but it hopes in June to secure a majority that will allow him to push through economic reforms for reviving an economy beset by high unemployment and sluggish growth.
Mr Macron's newly renamed "Republique en Marche" (the Republic on the Move) movement reacted warily to the announcement. Macron's 577 candidates are expected to be announced Thursday and Macron himself will be sworn in on Sunday. The newly elected French president set out plans in his manifesto to introduce a "Buy European Act" which would effectively restrict the ability of companies operating mainly outside of the bloc to access public procurement deals.
Some leading centrist Republicans appear ready to override the party hierarchy and work closely with Macron - one of them being former conservative prime minister Alain Juppe. If Le Pen had won the election and France had exited the EU, that "could've led to the collapse of the union", the official said.More news: Oil price tumbles on fears of oversupply
The rest will be defectors from the Socialists and right-wing Republicans and members of Mr Macron's movement and the allied centrist Modem party.
Jean-Paul Delevoye, head of the committee for selecting parliamentary candidates for Macron's party, said any would-be candidate must respect the party's rules and then the committee would review the application.
The Socialists, whose term in government comes to an end in tandem with the departure of President Francois Hollande, have traditionally disputed power with the center-right in France over the past half century.
As economy minister, a post he held for two years from August 2014, Macron had called for the merger of French auto giant Renault SA and its Japanese partner, Nissan Motor Co.More news: France claims Syria used chemical weapons
German Chancellor Angela Merkel on Monday praised Macron for the "courageous pro-European campaign" he waged against Le Pen's the far-right nationalist movement.
Other estimations also indicate that Macron garnered between 65 to 66.1 percent of votes, and Le Pen between 33.9 to 35 percent.
Macron's team said a "massive" hack had dumped emails, documents and campaign financing information online just before campaigning ended on Friday and France entered a quiet period which forbade politicians from commenting on the leak.More news: Everton skipper Jagielka uncertain about his future at club
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