Fast warned outsourcing firms they face civil and criminal liability if they or the organisations they provide services for do not have adequate software licences.
Nigel Roxburgh, director of the National Outsourcing Association, described Fast's approach as threatening. "There is a whole section on licenses in every outsourcing contract - I'm surprised Fast feels this is an area where companies are in breach," he said.
Suggestions by Fast's legal advisory group that licences may not allow firms to outsource were questionable, he added.
Robert Morgan, chief executive of outsourcing advisory firm Morgan Chambers, called Fast's approach "extremely high-handed" and said telling outsourcing firms to do due diligence and examine licences was "like teaching your grandmother to suck eggs".
"Most outsourcing firms would be extremely put out that there could be any accusation of this - outsourcers are very familiar with what they can and cannot do," said Morgan.
Eamonn Kennedy, senior analyst at IDC, said the move was probably an ill-thought-out publicity stunt. "The implication is that outsourcing firms are acting illegally in some way. I am not sure that a heavy-handed approach is really going to be all that productive," he said.