The Comptroller and Auditor General (C&AG) is to carry out a "pilot" investigation into the contoversial contract signed in 1987 between the Government and National Toll Roads, which operates Dublin's Westlink toll bridges.
The operation of the toll on one of the capital's busiest routes has come in for criticism by opposition parties and motoring representatives following a series of price hikes, most recently on January 1st.
Under the contract, NTR is entitled to an increase in rates each year.
C&AG spokesman Mr John Buckley
C&AG spokesman, Mr John Buckley, told ireland.com: "We are going to have a pilot study which will assess whether a full value for money investigation is warranted."
"We will be looking at the paperwork to see whether or not we could justify spending public money in doing this," he added.
He said the pilot investigation would be carried out by one individual who would start work on it within the next month. He said the pilot study would not be completed until the end of April.
He said the C&AG was carrying out the initial study after representations from "a number of TDs and haulage industry people" made representations.
Labour Party transport spokeswoman, Ms Roisin Shorthall, said the motoring public had to date paid out €310 million to National Toll Roads, or which the State received €65 million.
"A further €700 million is expected to be paid to NTR up to 2020 when the deal expires," Ms Shorthall added. "This represents a reutrn of approximately 2000 per cent".
It emerged this morning that NTR received State subsidies amounting to €6.4 million in the period 2002 to 2003.
The company was paid the money during the construction of the second Westlink bridge. Details of the payments, €2.9 million in 2002 and €3.5 million in 2003, are contained in the National Roads Authority annual report for 2004.
Suring construction of the second bridge the State sought a zero price increase for motorists because of disruption and was told this could only happen if the State paid a "shadow toll" for each vehicle using the bridge.