Rok saw half its market value wiped out following yesterday's profit warning.
Shares in the construction group plunged from 30p to just 11p, before rallying to 16.8p early this morning.
The firm announced that it had discovered “serious failings in the financial controls” of its Plumbing, Heating and Electrical division, and suspended finance director Ashley Martin.
"You end up making management decisions on numbers that are effectively made up”, chief executive Garvis Snook told the Daily Telegraph, adding that he felt “hugely let down”.
The City is already jittery about construction companies with large public sector workloads after a series of problems engulfed Rok's rival Connaught.