Trac has a five-year contract to maintain the external fabric of the Edinburgh building and has a full-time team based at the site.
But work was suspended on Friday following fears that roof anchor points used to attach harnesses were corroded.
Site investigations found possible problems with 14 of the 201 anchor posts used to attach access harnesses.
A Scottish Parliament spokeswoman said: “Routine inspections identified an issue with fixings on one anchorage point used by abseilers to carry out maintenance on Tower 3.
“We took the decision to suspend the use of all roof access systems. Our contractors Trac continue to work at Holyrood using alternative access methods.
“We have commissioned reports from our structural engineers and will consider options by the end of this month.”