The Mahon Tribunal has turned out to be slightly cheaper than expected.

The Public Accounts Committee (PAC) has heard that the tribunal is now estimated to have cost €159 million.

That is almost 20% lower than the costs previously estimated by the Department of the Environment.

The final chapter of the Mahon Tribunal report was published last year. It found that several Dublin county councillors received corrupt payments in exchange for their votes to re-zone lands in the south of the county.

The final chapter was initially withheld because of fears that it might adversely affect criminal proceedings being brought against the people involved.

The chapter dealt with attempts to re-zone around 130 acres of land at Carrickmines in South Dublin.

But the criminal corruption cases being brought against a developer and four county councillors collapsed last July when the main witness - lobbyist Frank Dunlop - was too ill to testify.