Anthony Scrivener QC, arguing on behalf of the former council leader, Dame Shirley Porter, the current leader, Miles Young, Barry Legg, now a Conservative MP, and the other accused, said that Mr Magill would not be able to appear to be open-minded when he hears the evidence at a public inquiry this month.
Yesterday, at Westminster Town Hall in central London, in an obscure procedure never used before, Mr Magill presided over a hearing to consider whether he should disqualify himself from the inquiry.
One of the councillors committed suicide shortly after Mr Magill's interim findings. If the other people are ultimately found guilty of wilful misconduct by selling council houses to gain votes at the expense of the homeless, they are personally liable to pay the pounds 21m, and may be disqualified from public office.
Mr Magill, a senior partner in accountants Touche Ross, called the controversial press conference on 13 January after an inquiry lasting four and a half years. 'My provisional view is that the council was involved in gerrymandering,' he said. He had used the words 'improper' and 'disgraceful' to describe what had gone on, language more appropriate to an Old Bailey judge passing sentence, Mr Scrivener said.
The summary of his report issued to the media had included a section Mr Scrivener described as 'self-laudatory', describing the work as unprecedentedly thorough. He had piled papers on his desk in front of television cameras to give the impression there was a strong case. He told Mr Magill the press conference and publication of interim findings were 'not only inappropriate, but it makes it difficult ever to withdraw those views. If you attempt to withdraw those views, you will look extremely foolish.
That is why judges and DTI inspectors eschew ever taking public views before the conclusion of a case'.
An audit of a council was a quasi-judicial procedure, Mr Scrivener argued, like a court, and like an inquiry into alleged insider trading by a Department of Trade and Industry inspector. In each case there was a presumption of innocence and the burden of proof lay with the prosecution.
He quoted the former Lord Chancellor, Lord Hailsham, who had commented after the auditor's press conference that it would be unthinkable for a judge to say after hearing the prosecution in a criminal trial that he was inclined to find the defendant guilty, but he would now hear the defence.
The Code of Auditing Practice stipulated the inquiries should be taken in confidence, and the 1982 Local Government Act said auditors should follow the code.
Mr Scrivener handed in a file of newspaper cuttings and played TV news bulletins to demonstrate that the auditor's report and remarks had been widely interpreted as an indication of guilt.
Mr Magill said he would give his decision next week.