"The Treasury has mentioned a figure of 20 billion to 30 billion euros (30 billion to 44 billion euros) in its first analysis," Fillon told Le Monde newspaper in an interview.
On Wednesday, President Nicolas Sarkozy's office talked about a loan 25 billion to 50 billion euros, while some lawmakers from Sarkozy's right-wing majority are calling for a loan of up to 100 billion euros.
Finance Minister Christine Lagarde has warned France must keep an eye on its deteriorating public finances as it decides how much money to raise for projects such as high-tech transport and third-generation biofuels.