The agency is to begin engaging with potential sponsors and financiers next month, to gauge their level of interest and the capacity of the market to meet the finance demands of the PPP.

The discussions will also involve consulting on its scope and commercial structure.

“The consultation will also examine how using a PPP approach could help the MetroLink project to meet its objectives, including in respect of sustainable outcomes and the use of green energy,” an update to be sent to organisations who have expressed an interest in being involved in the project said.

MetroLink is a proposed high-capacity, high-frequency rail line running from Swords to Charlemont, linking Dublin Airport, Irish Rail, DART, Dublin Bus and Luas services.

It will carry up to 50 million passengers annually, cutting journey times from Swords to the city centre to 25 minutes.

The project was confirmed in the recent revised National Development Plan as a key priority for the Government in meeting future public transport needs.

TII is to conduct the consultation process, assisted by the National Development Finance Agency, which is advising it on the finances of the project.

Further consultation is also planned by TII next year on its continued development of three main design-build contract packages for the core infrastructure.

The update also says that the preliminary business case will be presented for consideration by the Government shortly so that approval in principle can be sought.

“This approval will allow TII to proceed to the Project Design, Planning and Procurement Strategy stage and to apply for the Railway Order,” it said.

“TII is targeting the completion of all relevant planning material for MetroLink to allow a Railway Order Application to be made in the first half of 2022.”

TII is also planning to appoint a range of additional advisers and professional services for the project, as it progresses.

These include a client partner which will provide the skills and advisory services to support the procurement and delivery of Metrolink, an advance works engineering design service partner and a specialist financial advisor for the PPP.

An insurance adviser will also be sought between now and the end of the year along with a project delivery partners in late 2022 or early 2023.