SOUTH Australia's Legal Practitioners Board won't take action against a hit-and-run lawyer who killed a cyclist and fled to get legal representation.

The board's decision to find Eugene McGee had not engaged in unprofessional conduct when he killed Ian Humphrey in 2003 and fled has infuriated Independent Senator Nick Xenophon who wants its members sacked.

He's also called for a complete overhaul of the system for disciplining lawyers.

Mr Humphrey's widow, Di Gilcrist-Humphrey, complained to the board in April 2006 and received her reply this week.

In a letter from board member Tony Abbott, she was told it couldn't take action because McGee's conduct in the aftermath of the accident was not of such an "infamous nature" as to amount to unprofessional conduct.

"After hitting the cyclist, the practitioner did not stop his car or render assistance at the scene of the accident, he subsequently made several telephone calls, and later that evening he reported to police having arranged legal representation for the purpose," the board's letter said.

McGee's actions in the seconds after the crash had to be considered in the light of medical evidence at trial that said he was likely suffering from subclinical post traumatic stress disorder at the time of the collision.

Mr Xenophon says the board's "weasel words" were not good enough.

"According to the board, a lawyer can hit and kill a cyclist, leave him on the side of the road, even drive past the scene later, and not be guilty of unprofessional conduct," he said.

"It is disgusting."

Lawyers can't be trusted to adjudicate on their own, he said.

Senator Xenophon also slammed the board for failing to consider the evidence that McGee was a passenger in his brother's vehicle that drove past the crime scene while on his way to his lawyer, and failed to assist the police in their inquiries, when he clearly could have been able to.

McGee was not breath- or blood-tested for alcohol following the crash and was later fined $3100 for driving without due care.

His case sparked a royal commission which investigated how police handled the matter and led to conspiracy charges being laid against McGee and his brother.

Both were later acquitted of those charges.