A solicitor for CI╔ has said he has no knowledge of a letter Esat referred to when it told the Stock Exchange of its plans to construct a telephone network by laying cables along CI╔ railway lines.
Mr Michael Carroll told the inquiry he had "no record of any such letter" which firmed up the proposed venture between Esat and CI╔.
"We have checked our own documents and we have found no trace of it," he said.
Mr Carroll said he had found three references to the letter in the prospectus Esat submitted to the Stock Exchange in 1997 prior to the company's successful flotation on the Nasdaq index that year.
The inquiry heard one sentence in the prospectus stated: "Based on a signed letter of intent, the company (Esat) expects to use CI╔'s right of way to construct the network".
Mr Carroll said if such a document existed, it could have very serious implications. "I certainly want to get to the bottom of it."
Earlier, former Esat chief executive Mr Denis O'Brien and inquiry team member Mr Pat Rabbitte TD had differed on the importance of the letter.
Mr Rabbitte said it must have been the "cornerstone" of Esat's prospectus but Mr O'Brien said the idea was "laughable".
He said the Stock Exchange had evaluated Esat on the basis of its assets, which included infrastructure in all the main cities in the State, around £100 million in share capital, a recognised brand-name and customers.
He said Esat was "breaking through" in the telecoms market and had revenue of $10-15 million a year which investors could see reaching $200 million a year five years on.
Esat had delivered on its promise, he said, recording early growth of up to 17 per cent every quarter.
Later when Mr Carroll gave evidence, however, he said he agreed in general with Mr Rabbitte's assessment of the letter's importance.
"I think Mr O'Brien understated it. It must have significance because it is set out as part of the infrastructure that Esat is offering as part of its package."
Yesterday's session of the inquiry also heard further evidence from Mr James Gahan, former head of the CI╔ property department, who repeated his belief that offers from companies other than Esat to partner CI╔ in a telecoms venture were sufficiently explored.
The inquiry had previously heard that CI╔ had up to 10 other offers but carried out detailed discussions only with Esat and called in outside expertise for advice only after heads of agreement were signed with Esat.
Mr Gahan objected to suggestions by Mr Rabbitte that he and his CI╔ colleagues were unqualified to evaluate the offers for themselves and were "flying by the seat of their pants".
"It's not fair that because you didn't work in the private sector, you were an idiot," Mr Gahan said.