Boss Carlos Ghosn went on prime time television to apologise "personally and in Renault's name", but said he had turned down an offer by his number two, operations chief Patrick Pelata, to resign over the debacle.
Renault officials quickly sacked the three managers in January, saying publicly they had proof they had been selling secrets on the electric technology which is expected to change the car industry.
The French government had branded the affair "economic warfare" and some pointed the finger at China, drawing an angry denial from Beijing.
Ghosn and Pelata said in a statement they would meet with the managers concerned as soon as possible and "make reparations" after revelations that the source of information alleging the spying may have been a fraudster.
Appearing on France's TF1 channel, Ghosn said he and Pelata would forgo their 2010 bonuses and that Renault would review its security procedures and take disciplinary measures against three implicated security employees.
The car manufacturer said it would be a civil party in an investigation into alleged fraud by an organised gang announced by Paris prosecutor Jean-Claude Marin earlier Monday, which apparently spurred the apology.
"We are looking at possible fraud," Marin told journalists. "It seems that Renault was perhaps not the victim of indelicate employees but of possible confidence tricksters."
The prosecutor's probe came after three employees responsible for security were detained on Friday and Saturday for questioning.
Two of them were later released without charge and the third, Dominique Gevrey, may face fraud charges over the espionage charges that rocked Renault in January.
The scandal returned to haunt Renault again when a source close to investigations said this month that the claims had led nowhere after police found no trace of bank accounts in Switzerland and Liechtenstein that the accused men were alleged to have held.
Investigators detained Gevrey as he was about to board a plane for Guinea despite the fact that Renault had declined his holiday request.
"He said he would reveal during the investigation the identity of the source and the bank accounts but all his explanations so far have turned out to be false or inaccurate," Marin said.
Renault has already spent 310,000 euros ($435,000) for information on the spying allegations, funds believed partially held in Spain and Dubai that investigators are trying to trace, the prosecutor said.
"Renault had almost 400,000 euros waiting, as asked for by Gevrey or the intermediary," Marin said.
"Gevrey said that his source could give him the forms with signatures opening these accounts (in Switzerland and Liechtenstein) in exchange for the modest sum of 924,000 euros."
Another top Renault manager was sacked for similar reasons over a year ago after he was accused of having opened a bank account in his wife's maiden name in the southeastern city of Grenoble.
"There also, investigations showed that the manager did not have an account in Grenoble," Marin said.
Nevertheless, the prosecutor said that it was still possible that Renault had been the victim of industrial espionage or simply of a bid to destabilise the car manufacturer.
Lawyers for two of the sacked managers, Matthieu Tenenbaum and Michel Balthazard, said their clients were prepared to meet Ghosn, although Balthazard's lawyer said it was "inconceivable" he work again for Renault.
There was no immediate word from the third sacked manager, Bertrand Rochette.
The lawyer for the man sacked over the alleged Grenoble account, Philippe Clogenson, said he regretted the fact that Renault had not also apologised to his client.
