But instead, Banbrook told the court that he did not agree with the Crown's summary and fired his lawyer.
That created more delays ahead of an impending disputed facts hearing which in the end never went ahead, Mr Symon said.
"In the Crown's submission, Mr Banbrook effectively adjourned the sentencing until it suited him ... Had the sentence proceeded in June, he would have been subjected to a sentence over the Christmas break."
He said Banbrook had shown little remorse and even asked for his passport back after pleading guilty so he could go on holiday to Fiji - something out-of-pocket investors would have found hard to swallow.
Mr Symon said Banbrook was the only independent director because fellow directors Trevor Alan Ludlow and Carol Anne Braithwaite were in a relationship at the time.
He said had Banbrook taken the basic steps required of a director, he would have known the prospectus contained misleading passages.
"Now he accepts that he was grossly negligent."
Banbrook's lawyer Harry Waalkens QC said the case was delayed because his client did not accept the Crown's assertion that he knew about related-party loans.
Mr Waalkens said it was significant the allegation had been withdrawn from the Crown's summary.
He said Banbrook had no intention of delaying the proceedings and only wanted his passport back so he could visit his son in Sydney.
Mr Waalkens also said he had never been dismissed by Banbrook but withdrew because the week-long disputed facts hearing would have cost too much.
"This is not a dishonest man, this is a man who has been caught up in the dreadful finance company collapses."
He said Banbrook now faces disciplinary action from the Law Society.
"He is going to suffer a major fall from grace."
In sentencing, Justice David Collins said Banbrook had neglected to question other directors about the reliability of statements in the National Finance prospectus sent to investors.
Justice Collins had started with a prison sentence but took time off his sentence to reflect Banbrook's previous good record, his remorse and his reparation payment.
National Finance went into receivership in 2006, owing investors $21 million. Some investors have recovered 49c in the dollar.
Ludlow is serving a sentence of six years and four months in jail after being convicted of charges laid by the Serious Fraud Office and the Financial Markets Authority. He was found guilty of defrauding investors of an estimated $3.5m.
Braithwaite was last year found guilty of making untrue statements in a National Finance prospectus, released in September 2005. She was sentenced to home detention.
