Southend City Council is investigating allegations of bullying and fraud made by a whistleblower who claims to have been suspended for raising the issues.
Opposition councillors want Government inspectors to investigate the serious claims.
They are also demanding senior executives who were made aware of the allegations but failed to act are suspended.
The whistleblower, a senior executive director, compiled a lengthy dossier of grievances and formally invoked whistleblower status to the director of legal services, Giles Gilbert, in March.
The director has been suspended however, and is now facing an investigation himself.
It is believed that the whistleblower raised issues over breaches of procurement rules, contract procedure, and fraud within the team.
The allegations were leaked to Private Eye which named Southend in its Rotten Boroughs column this week.
Councillor Tony Cox, leader of the Conservative group, said: “In March last year, I was made aware of serious allegations and a number of alleged wrongdoings within the council via a whistleblower who I will not be naming.
“As per the council’s policy, I referred the allegations to the council’s monitoring officer and head of internal audit.
“The allegations are deeply alarming and incredibly serious and I hope they will be investigated thoroughly.”
Cllr Cox added: “I had no intention of making political capital during the election campaign and I’m disappointed that the complainant has been leaked along with discussions I have had with the monitoring officer in relation to the allegations being looked at by a potential meeting of the appointments and disciplinary committee.
“I have long had concerns, which are in the public domain, with procurement, poor quality cabinet papers and governance.”
The group is set to approach Rochford and Southend East MP James Duddridge to request Government inspectors investigate the allegations.
A council spokesman said: “While the council cannot comment on individual staffing matters, the council has appropriate procedures and processes in place to deal with such matters.”