An internal document passed to the Government by management at CIÉ has put the cost of breaking up the company at more than € 500 million.

The executive board of CIÉ, after reviewing the operations of the three constituent companies, highlights the significant costs of breaking the company up, a proposal supported by the Minister for Transport, Mr Brennan, but vehemently opposed by unions.

The issue of the future of CIÉ and Aer Rianta is beginning to cause tensions in Government and among the powerful public sector unions.

Last night, a meeting attended by the Taoiseach ended without agreement between the unions and Mr Brennan on the substantive issues, although officials, including the Secretary to the Cabinet, Mr Dermot McCarthy, are to meet again to see if some of the more contentious matters can be defused.

Mr Brennan has rejected claims that the break-up could cost the Exchequer huge sums. He believes selling CIÉ's non-essential properties should cover any restructuring costs.

According to the document, any break up would have to involve wiping out CIÉ's group debt of € 234 million. It also claims that € 100 million of costs would be incurred because each CIÉ company would have to manage compensation claims on its own.

The document suggests that almost €250 million would be needed to buy out employee's existing terms and conditions. About 4,700 CIÉ employees, hired before 1987, have so-called "letters of comfort" from the company, which say that if the parent company is wound up workers must remain on the pay roll or be compensated following negotiations with their union.

The document was passed to a meeting some weeks ago of the Restructuring Implementation Group at the company. Representatives of the Department of Finance and the Department of Transport were present and received copies of the report.

Meanwhile, last night's top-level meeting attended by the Taoiseach, Mr Brennan and ICTU general secretary Mr David Begg, failed to break the log-jam.

According to sources, there was a "frank exchange of views", with Mr Brennan emphasising that, while union concerns were important, the competitiveness of the economy was also key. Unions agreed with this but said his plans for public transport would not necessarily improve national competitiveness.

The internal document says any restructuring attempted by Mr Brennan must take into account the company's debt position, most of which resides with Iarnród Éireann.

The document also questions plans to use the company's property portfolio to pay for the restructuring. It says there are more than 100,000 title deeds involved. "The transfer of title to the subsidiary companies could take up to two years to achieve and would clog up the Land Registry office and incur significant costs during that time."