The United States government appeared to be unaware of the source of funding for Declan Ganley's Libertas movement in the Republic -- despite widespread speculation it was being secretly backed by the US.
A confidential US embassy cable indicates US diplomats were as curious as Libertas' political opponents to know the source of the party's funding.
The cable, written by the US deputy chief of mission in Dublin, Robert Faucher, was circulated to the office of then US Secretary of State Condoleezza Rice and American embassies across the EU in March 2009.
Mr Faucher wrote that Mr Ganley "refuses to come clean" on how Libertas funded its anti-Lisbon campaign.
He said this had "fuelled conspiracy theories" about who was backing Mr Ganley, who is still the chairman and chief executive of Rivada Networks, a US defence contractor specialising in military telecom systems.
These "conspiracy theories" included claims, denied by Libertas, that the organisation had been backed by the CIA or US government neoconservatives who were opposed to the emergence of a united Europe that could challenge US power.
According to Mr Faucher's cable, Rivada provided communications technology to the US military's northern command, as well as the National Guard in 16 states and three US federal bureaus.
He said the contracts were "alleged" to be worth over US$200m and noted five of the founding seven members of Libertas were Rivada employees
Mr Faucher told diplomat colleagues Libertas claimed to generate 10pc of its funding from internet donations, while the remaining 90pc came from unnamed wealthy individuals.
He said the party insisted it was unwilling to publish the identities of its donors because it had concerns they would be harassed or would face undue pressure from the political establishment.
A separate cable, also from March 2009, reinforces the impression that US officials were keen to know the source of Libertas' funding.
In it, Mr Faucher noted that while Mr Ganley had informed the Standards in Public Office Commission (SIPO) that he gave a personal loan of 200,000 euros to the anti-treaty campaign, he failed to provide further information sought by SIPO as to the nature of the loan.
The diplomat also stated SIPO had received no reply to questions about other loans Libertas may have received.