The investigation report into a controversial email sent under the direction of Norfolk County Council leader Derrick Murphy will not be made public – despite calls for it to be brought into the open.

The email, which was sent by political assistant Kevin Vaughan to BBC Radio Norfolk, appeared to undermine West Norfolk Council leader and fellow Conservative Nick Daubney over the King's Lynn incinerator.

Last week the findings of an independent probe into the incident were released and found it was Mr Murphy who had asked for it to be sent to Radio Norfolk presenter Nick Conrad.

At a meeting of the full council today, a number of councillors asked for the full report to be made available to them so they could read it for themselves.

But David White, the authority's chief executive, insisted the details of the official investigation were confidential and that no-one beyond those directly involved in the report had seen it.

Reading a statement to a meeting of the full council yesterday, he said: 'It is very important that council understands why the report of the independent investigator, John Anslow, is and will remain confidential.

'The report was commissioned by the county council when the email of the political assistant Kevin Vaughan came to light following a Freedom of Information Request made on April 24. It was commissioned under the council's employment processes to review the alleged accusations against a member of council staff.

'Only those involved in those employment processes have been authorised to have sight of the investigator's report. In addition to the independent investigator, Kevin Vaughan, and his representative, only eight people – all senior officers of the council involved in the investigation and the subsequent employment procedures – have had sight of the report. As always in internal employment matters, the council must respect the legitimate rights of the employee.

'The council will not release a copy of the report.'