The Faculty of Advocates believes a bill proposed by Labour MSP Patricia Ferguson will make the process longer, more complex and costlier.
Ms Ferguson is proposing an overhaul of the FAI system, focusing on the victims and families, and ensuring that all recommendations are enforceable.
The Scottish Government is committed to making changes to FAIs and said it would consider Ms Ferguson’s proposals once the consultation was finished.
However, in its response, the faculty warned: “We have grave concerns about the creation of a statutory offence based on failure to comply with a recommendation which can be made on the basis of uncorroborated evidence, and from which there is no right of appeal.
“We are concerned that the imposition of mandatory compliance with recommendations in this way has the real potential to turn FAIs into examples of the most adversarial litigation.
“The end result of this is likely to be that FAIs are made lengthier, more complex and more expensive.”
It also criticised plans to extend legislation on work deaths to cover industrial diseases.
“In the case of industrial diseases, it is very often the case, due to long latency periods, that the death will occur long after lessons have already been learned about the dangers posed by the causative agent and the precautions required to avoid exposure,” the faculty said.
Ms Ferguson’s bill is designed to speed up the process, an aim the faculty backs.
Last year, the daughters of a man who died during a botched dialysis treatment were scathing about the Crown Office after waiting six years for a fatal accident inquiry verdict.
Andrea Little and Beverley Taylor said at the time: “It has taken over six years since our father died for us to have these answers and in our opinion the stress and the toll that has taken on our everyday lives and our families is totally unacceptable. No family should be made to suffer in this way for such a sustained period of time.”
Lord Cullen has carried out a review of FAIs and made many recommendations, which the Scottish Government says it plans to enact.
Some of them have already been taken up by the Crown Office, such as the creation of a specialist FAI team.
Lord Cullen suggested individuals or bodies targeted in an FAI recommendation should have to respond within a given timeframe.
He also said the recommendations and responses should be made publicly available on a Scottish Government webpage.
However, he stopped short of calling for penalties for noncompliance.
Ms Ferguson believes it should be classed as an offence punishable through a fine or up to six months’ imprisonment.
And she says she is not deterred by criticism from the faculty. Legislation is to be brought within two years.