The Italian government has revised the rules governing the spin-off of Alitalia in a move that has surprised bidders and could delay the sale of the loss-making Italian airline.

Padoa Schioppa, Italy's economy minister, said he would send letters to bidders outlining changes to the rules governing the auction. Alitalia, which is 39.9% owned by the government, is losing €1m ($1.35bn) a day.