Mr Finn and Pallion Housing agreed to pay a £119,000 settlement in what was believed to be at the time the UK's biggest Internet defamation payout, after the High Court hearing in April 2008.
They were told to hand over the six-figure sum to Peter Walls, boss of gentoo, formerly Sunderland Housing Group.
The payout came after anonymous statements were made on the Dad's Place website and in other publications, which over a two-year period made serious allegations about gentoo and its managers.
Pallion Housing went into administration on July 22, 2009.
But it is understood that £409,000 in costs are still outstanding, which were accruing interest at a rate of £805 a week.
Andrew Taylor, deputy chief executive of gentoo group, confirmed that gentoo had petitioned for bankruptcy against John Finn at Newcastle Law Courts on Wednesday.(Read more)