David Horgan, the managing director of Petrel Resources and a Sunday Tribune columnist, told his company's AGM last week that he believed that the advice, from the department of defence, ensured that the company retained control of an exploration block containing up to five billion barrels of oil despite the overthrow of the regime.

The department, however, along with the department of foreign affairs, which was also named by Horgan, said they could not locate records of any advice given to Petrel while a third department, the department of enterprise, trade and employment said that it did not provide any advice to Petrel in relation to the block.

But Horgan said that the advice, along with subsequent Irish government lobbying of the Provisional Coalition Authority, established by the US after the invasion and subsequent Iraqi governments, meant that Petrel was confident of retaining control of the block.

"The advice from the government was very straightforward, " said Horgan. "They said: 'we will back you. We will not send in a ministerial delegation but what you should do is agree everything technically with the professional technocrats, the Sir Humphreys, who will always be there'".

"'Don't link yourself irrevocably with the current regime because they may not have a long life expectancy. And that advice turned out to be exactly right.'" Speaking subsequently to the Sunday Tribune, Horgan said that the government's intervention was crucial as it persuaded him not to attempt to negotiate directly with Hussein and his regime. Despite this, Petrel concluded a deal with the Iraqi government in December 2002.

"It was a difficult call and at the time, it wasn't as obvious as it now seems but they read it correctly and I think no other government would have been quite so forthcoming with advice."

Horgan said Petrel had received some informal indications from the current Iraqi government that it would recognise its legal right to the block and would start negotiating new exploration terms with it later this year.

"That's not really a problem because terms under new law will be better than the terms under the old law. To put it bluntly, they are too good, the peaceniks and the NGOs are right. But the government is only giving it to us at those terms due to their straitened circumstances."

A spokeswoman for the department of defence said that it could not locate records of any advice provided to Petrel. However, she said the department would give advice if appropriate on a case-bycase basis. The department of enterprise denied Horgan's claims that the government lobbied successive post-war Iraqi governments on the behalf of Irish companies operating there.

"If lobbying. . . did take place, it did not take place at the behest of this department, " said a spokeswoman.

The department of foreign affairs said that "while many Irish companies expressed an interest in early 2003 in engaging in reconstruction or commercial activities in Iraq, there is no record of any direct contact between the department of foreign affairs and Petrel Resources, or of specific lobbying to the Coalition Provisional Authority."