Desperate efforts by the Italian government to find a buyer for Alitalia ran into deeper trouble on Friday as shares in the lossmaking airline plunged on the Milan stock exchange and unions threatened wildcat strikes over the Christmas holidays.

In addition, Consob, the Italian stock market regulator, launched inquiries into possible market abuse involving Alitalia shares following leaks to the media of the share price offered by Air France-KLM and Italy’s Air One, as well as a third expression of interest which was possibly a hoax.