World Bulletin / News Desk
Valls said he would vote for Macron in the April 23 first-round ballot.
The former prime minister argued it was the only way to block far-right National Front candidate Marine Le Pen -- currently second in opinion polls -- from winning in the second round on May 7.
It was the “choice of reason," Valls -- who lost at the Socialist Party primary in January -- told French broadcaster BFMTV.
"I'm not going to take any risks; I will vote for Emmanuel Macron," he added.
Speaking on Europe 1 radio at the same time, Macron thanked Valls for his support but insisted on the need of the "renewal of faces".
Polls show Macron and Le Pen progressing to the second-round run-off on May 7, where Macron is currently predicted to win by about 20 percentage points.