After a day of speculation that Marchionne's successors would be appointed, a statement from Fiat confirmed that the Italian's health had deteriorated enough for immediate action to be taken.

A statement said: "Fiat Chrysler Automobiles N.V. communicates with profound sorrow that during the course of this week unexpected complications arose while Mr. Marchionne was recovering from surgery and that these have worsened significantly in recent hours.

"As a consequence, Mr. Marchionne will be unable to return to work."

As a result of the unexpected developments, the Fiat board elected to fast-track a succession plan that was originally being put in place for the end of this year when Marchionne had been due to step down.

A proposal has been put forward for Mike Manley, head of the Jeep company, to be proposed as the new Fiat CEO at the next shareholder's meeting.

In the meantime, Manley has been given full authority to act with all the powers of the CEO in Marchionne's absence.

At Ferrari, Fiat heir John Elkann has been named as the new chairman and the Maranello company has it has said that he will propose to shareholders that former Philip Morris chairman Louis Carey Camilleri become the new CEO.

Camilleri has already been given the powers to ensure the company's operations continue until he has been formally appointed to the role.