The decision was reached following consultation with the 46 affected employees. It will see the scheme, which is part of the States of Guernsey's Public Sector Pension Scheme (PSPS), closed to new contributions from 1 July 2014.
The closure follows the commission's earlier decision to shut the scheme to new members from 1 January 2008.
The commission said it very much appreciated the cooperation and understanding of affected staff.
Director General William Mason, pictured, said: 'Sadly it has become virtually unaffordable for any organisation which wishes to have a solvent future to maintain defined benefit schemes which allow members to retire in their sixties with, on average, at least twenty years of retirement ahead of them.'
The commission said current projections from actuaries showed that the costs and future liabilities of the scheme were continuing to increase.
It said it had also taken into account other considerations, including the fact that most firms within the island's finance industry had largely phased out their defined benefit pension schemes.
