"I don't have to prove my loyalty to the president of the Republic," Valls told RFI while on tour in Côte d'Ivoire.
But a couple of days earlier he had spoken of party members' "shame" and "anger" over a book of interviews with Hollande, Un Président ne devrait pas dire ça (A President shouldn't say that), in which the president talks perhaps a little too frankly about his comrades, French judges and various other questions.
'He's our Trump'
Publicity surrounding the book appears to have pushed Hollande even lower in the polls.
And it has cost Hollande some political friends, among them the president of the National Assembly, Claude Bartolone, who commented that the president had a duty to be silent on some matters.
With one poll showing Hollande at under 10 percent satisfaction rating, other Socialist MPs have gone further.
"He's our Trump," one told Le Monde newspaper, anonymously of course.
Valls told RFI that he would never do anything to add to the disorder and told his colleagues that they are not in the playground.
Hollande still boss
But his earlier remarks prompted Hollande loyalist and government spokesman Stéphane Le Foll to remind the party, including the prime minister, that Hollande remains the boss.
The crisis is so deep that some Socalists are now asking whether Hollande should stand in the Socialists' primaries, even though it was not even certain they would take place until recently since it was assumed the incumbent would be within his rights to insist on being candidate.
Party supporters disillusioned
The problem is that neither Valls, who appears unready to stand unless Hollande backs out, or any other potential candidate would do much better, such is the disillusion with the government's record among the party's traditional supporters.
Some polls have even shown hard-left candidate Jean-Luc Mélenchon beating Hollande, although he, too, has fallen out with his erstwhile allies in the Communist Party.
Right v far right in second round
All polls now show a second-round standoff in 2017 between the mainstream right Republicans, who have yet to pick their candidate, and the far-right's Marine Le Pen.
The Socialists had hoped that the acrimony between former president Nicolas Sarkozy and former prime minister Alain Juppé, not to mention sparring between other Republicans hopefuls, would distract attention from their problems.
But Hollande's book, no doubt planned as a boost to his chances of standing again, has had the opposite effect, hogging the headlines and sowing disunity in the party.
"The fate of the reformist left is in the balance," Valls told Le Monde.
If it is "atomised" in the presidential election it will "leave history", he concluded.