The Government is planning new legislation that will give the State the power to claim ownership of land underneath private property.
The Infrastructural Bill, which has been drawn up by the Department of Transport, is designed to reduce the estimated €4.8 billion cost of the proposed metro from the centre of Dublin to the airport.
The Irish Times understands that the Minister for Transport, Mr Brennan, will discuss the proposed Bill at the special all-day meeting of the Cabinet in Farmleigh tomorrow.
Frustration with delays and sharply escalating costs associated with rolling out major infrastructure projects have prompted the legislation, according to Mr Brennan.
The €4.8 billion estimate for the 11.5-kilometre city-centre to airport line remains unacceptable, he says.
"It's too dear. I can't do it for that price. I have asked the Railway Procurement Agency to see can they get some better prices."
However, Mr Brennan stressed the Government was committed to the full metro plan drawn up by the Dublin Transportation Office.
"The Metro is a nine-, or 10-phase development and it is important that we don't think just in terms of an airport link. The airport link is phase one of that development."
Plans to give the State the power to claim ownership of land needed for development comes after confirmation that nearly 10 per cent of the €675 million cost of the Luas is expected to go on land-acquisition costs. Securing the rights to underground property could save the Exchequer tens of millions of euro.
For example, the contract price for the Dublin Port tunnel is €450 million, but the project cost, including CPOs, environmental impact studies and pre-tender design is €650 million.
In an interview to be published in the Engineers Journal, Mr Brennan said he was drawing on the experience of other countries, such as Spain, in drawing up the infrastructure bill - Madrid recently built a metro for €600 million. Explaining the difference in cost between the two similarly-sized projects, Mr Brennan pointed to land ownership as a key point.
"They own the land underground which we don't - and they have much shorter time frames [for completing infrastructure projects]. They also cut back on the involvement of the legal procedures and lawyers."
A senior legal source told The Irish Times there would "undoubtedly be a constitutional question to be referred to the Supreme Court under Article 26" on the move to acquire underground property rights. He said the traditional interpretation of property rights was that all the land above and directly below was part of the property.
Mr Brennan said the Bill is expected to contain changes to Compulsory Purchase Orders, reducing the time allowed to lodge appeals. He also hoped to introduce laws freezing land prices along an infrastructure route as soon as that route is chosen.