Top Liberal Arthur Sinodinos breached rules Apologies ... Arthur Sinodinos. SENIOR Liberal senator Arthur Sinodinos has been caught breaching parliamentary rules by failing to declare six company directorships during his 15 months in the upper house. The former chief-of-staff to ex-prime minister John Howard last night admitted that his register of pecuniary interests contained the significant omissions after inquiries by The Daily Telegraph about the anomalies. "I apologise unreservedly to the senate and to my party colleagues for these oversights," he said. I believe at no stage were there any matters arising from these directorships which may have occasioned a conflict of interest. Company searches revealed Senator Sinodinos failed to declare five current directorships, including with an aged healthcare firm whose directors include former Liberal minister Santo Santoro, who quit in disgrace over omissions from his parliamentary register. Senator Sinodinos also failed to declare a position with Sydney-based firm Firestick ICT Pty Ltd and with Liberal Party-linked outfits Bunori Pty Ltd, Liberal Properties Ltd and Liberal Asset Management (Custodians) Ltd. It can also be revealed he did not declare a year-long former directorship with not-for-profit business leadership group, The Octant Foundation, which ended late last year. The revelations come after the senator's business interests came into focus this week when he backed away from claiming a potential multi-million-dollar stake in an infrastructure company after it was linked to Labor powerbroker Eddie Obeid. Senator Sinodinos is considered a rising star and almost certain to win a ministerial position in an Abbott government. One of his fellow directors at Sydney healthcare company Move2Live is Mr Santoro, a registered lobbyist and former aged care minister. It was reported at the time Senator Sinodinos, as Mr Howard's chief-of-staff, had quizzed Mr Santoro a year before the scandal over his interests. Senator Sinodinos may now face a privileges committee inquiry over the omissions, with punishments for knowingly providing incorrect information to parliament including jail or fines. He told the senate he would resign the unpaid directorship of the health business, Move2Live. He said would also resign from the Firestick ICT position, blaming a mix-up after he recently resigned from a linked firm, Aboriginal Employment Strategy, but not its related IT firm. "I am disappointed it took a journalist to remind me of these directorships," he said. Senator Sinodinos had updated his register only three days ago.