Minister for Public Expenditure Paschal Donohoe did not declare his directorship of a company when he was a senator in 2009.
Mr Donohoe did not include his board membership of ExSite Politics on the register of interest of members for the Seanad.
However, he did declare his directorship of a related company called ExSite Communications, which shares the same address in Dublin's Baggot Street.
The story first appeared on The Ditch website.
In Mr Donohoe's declarations of members interests for 2009, he stated he was a non-executive director of ExSite Communications on a "pro-bono" basis.
On the declaration, it states that ExSite Communications is engaged in website design.
In a statement his spokesperson said that he served for nine months on the board of a company called ExSite "which was a start-up company, 14 years ago."
She added: "He did not benefit in any way from the board membership. He has contacted the company owner about the matter."