The French government has started the privatisation of Gaz de France in what will be the biggest initial public offering this year, worth up to €4.5bn ($5.4bn) and valuing the company at up to €23.4bn.

Calyon, Lazard-Ixis, Merrill Lynch and SG Corporate and Investment Banking, which are running the offering, have set an indicative price range of €20.7 to €24 per share for institutions, with a 20 cent discount for retail investors.