Former Fianna Fáil TD Mr Liam Lawlor has been accused of giving false evidence in an affadavit to the High Court.
Mr Lawlor told the High Court in July 2001 he received £625,000 from the sale of an acre of land beside his home in Somerton, Lucan, to a London-based property company.
However, the tribunal has established the price on the contract signed almost a year earlier was £690,000 and that Mr Lawlor received a further under-the-counter payment of £135,000 as part of the deal.
Tribunal chairman Mr Justice Alan Mahon put it to Mr Lawlor that the evidence he gave in the affadavit was "utterly false" and "completely misleading".
Mr Lawlor claimed the deal had not been totally agreed when the affadavit was drawn up and the sale price had subsequently changed.
Judge Mahon said: "This has to be unbelievable".
Earlier, Mr Lawlor accused the tribunal of wrongly using documents to manipulate proceedings against him in the High Court.
Mr Lawlor, who has been in jail three times for failing to co-operate with tribunal, said today he had sought documents from the office of solicitor Mr Noel Smyth and had failed to receive them.
He claimed the documents were instead sent to the tribunal directly and then used selectively by the tribunal's lawyers in the High Court against him.
Judge Alan Mahon told Mr Lawlor he would prefer if he did not make such allegations because "they were untrue".
The tribunal rejects Mr Lawlor's version of events, accusing Mr Lawlor of failing to disclose documents that he personally retrieved from Mr Smyth's office.
Mr Smyth acted on Mr Lawlor's behalf in his dispute with another solicitor, Mr Caldwell.
Mr Lawlor is alleged to have taken original copies of documents from Mr Smyth's office on the condition that he would return copies to the office. At the time Mr Lawlor insisted the tribunal required the files urgently.
The tribunal was shown a number of letters from Mr Smyth's office to Mr Lawlor complaining that he had taken the original documents without returning copies and that he had failed to pay outstanding fees.Mr Lawlor says he retrieved only one file from the office and disputes he had any undertaking to return copies.
