Staffordshire Police launched an investigation in 2010 after a number of complaints over tendering processes
The force told the BBC it submitted a report to the Crown Prosecution Service, which has decided not to prosecute.
The four men, who were due to answer bail this week, have been released from their conditions without charge.
Two other men who had been arrested in connection with the investigation were previously released from their bail conditions without charge.
Staffordshire Police said it had carried out a “protracted investigation” over the complaints.
The CPS is still reviewing evidence from the force concerning a related investigation into the tendering processes linked to particular redevelopment projects undertaken by the council in 2008, a police spokesman said.