The Italian press believe the move that could open the way to the creation of a full-fibre national network.

Enel, which jointly controls Open Fiber with state lender CDP, said it had given a mandate to its CEO to sell between 40- 50 percent of the company to the Australian fund by June.

It said Macquarie would pay 2.65 billion euro ($3.3 billion) for a stake of 50 percent but added it included the transfer to the fund of a shareholder loan worth 270 million euro.

The deal also includes a series of earn-out clauses, including one linked to the positive conclusion of a legal dispute between Open Fibre and phone incumbent Telecom Italia (TIM).

A sale by Enel of its stake could clear the way for a government-sponsored plan to merge Open Fibre with the last-mile grid unit of TIM and create a unified ultrafast broadband network.

Enel said another earn-out clause in the agreement revolved around implementation of this network.

CDP, which is the second-biggest shareholder in TIM behind French media giant Vivendi, would emerge as a prominent investor in the combined entity.

Rome wants Macquarie to buy less than 50 percent so CDP, which has a right of first refusal on the Enel stake in case of a sale, can take control of Open Fibre and make sure the blueprint for a single network is respected.

Enel said any deal to sell its whole 50 per cent stake would be subject to Macquarie and CDP sharing “modification of certain aspects that currently regulate the governance of Open Fibre.”

The utility also said the sale was conditional on Open Fibre allowing Macquarie to share due diligence data with a small number of co-investors so it could syndicate the asking price.