Patrick Vieira said he considered "serious and scandalous" remarks allegedly made by Blanc at a November meeting where reports say French federation officials discussed the idea of introducing quotas for African and Arab players in youth teams.
Lilian Thuram has also been critical of Blanc along with former goalkeeper Bernard Lama.
Three other world champions - Christophe Dugarry, Bixente Lizarazu and Emmanuel Petit - have stood up for Blanc.
The Journal du Dimanche website aid French Sports Minister Chantal Jouanno had called the coach, on holiday at a spa in Merano in northern Italy, and "has affirmed her support for him."
The coach is "wounded by the remarks towards him" but did not mention a resignation, she added.
Blanc is due to appear before two inquiries set up by the ministry and the federation which could decide his future.
Jean-Pierre Louvel, president of the union of professional clubs (UCPF), attacked federation president Fernand Duchaussoy, who is hoping for a new term of office in June's elections.
"Anything can happen now. The federation does not have a boss at the helm. I find it very serious what is happening. We must purify this," he told Reuters.
AGAINST DISCRIMINATION
Based on an alleged transcript of the Nov. 8 meeting released by investigative website Mediapart Blanc made controversial comments seemingly in favour of the quota plan.
"It's outrageous. These are serious remarks," former France captain Vieira said in an interview with Le Monde.
"You can tell me what you want, but nobody was trapped at this meeting."
Blanc has apologised for uttering remarks which were "out of context" but could "offend some sensibilities".
"But, being suspected of racism or xenophobia when I am against any form of discrimination, I can not stand for," he added.
His defence strategy has not convinced Lama.
"What bothered me with Laurent is that he initially denied it and afterwards he apologised. That's what bothers me most," he said on BFM TV.
Dugarry went after Thuram for criticisinig the coach.
"I think he wants to divide French football. I find him hard, aggressive towards Laurent Blanc," Dugarry told L'Equipe.
Lizarazu told RTL that Blanc had never had racist attitudes.
"If the question is should Blanc resign? I reply no," he said.
Petit said: "the French Football Federation does not deserve a guy like Laurent Blanc at its head.
"I think he has a strong personality but I think the case will not leave Laurent Blanc or the people who participated in this story unscathed," he told RTL.
