They say if the rule is scrapped, there is a risk police investigating crimes may stop looking for corroborative evidence, weakening the case against the accused.
Their arguments emerged in new documents submitted to the Scottish Government's consultation on the Criminal Justice Bill, which includes the proposal to remove the centuries-old feature.
It requires evidence in a trial to be corroborated before an accused can be convicted and prevents conviction based on one person's testimony. Ministers want to remove the requirement to increase the chances of conviction for rape and domestic violence offences.
But, responding to the consultation on the Bill, the Faculty of Advocates said its removal could actually lead to fewer convictions for rape and sexual offences as without the need for corroborative evidence, police investigating crimes might not seek it out.
"There is no evidence to support the contention that the abolition of the requirement of corroboration will result in an increase in the proportion of sexual offence cases which result in a conviction," it said.
As the law stands, the only cases which go to trial are those in which there is corroboration. The Faculty said that, even with a requirement for corroboration, the number which resulted in acquittal reflected the difficulties in sexual offence cases.
"It is a fallacy to believe that by prosecuting cases even where there is no corroboration, the proportion of successful cases will increase. The reverse is more likely to be true," it said, adding: "The abolition of corroboration may disadvantage victims of crime. Cases may be prosecuted where there is ... no strong likelihood of success.
"If there is no legal requirement for corroboration, there is at least a risk that the police will not investigate with a view to finding corroborative evidence if it exists. This could mean that cases which currently result in conviction will, following the change, result in acquittal."
The Glasgow Bar Association, which represents about 400 criminal defence lawyers, said it was "not convinced that removing the requirement for corroboration would significantly increase the conviction rate". Lawyers' arguments against removing the requirement are due to be expanded on tomorrow when representatives appear before MSPs.
Murdo Macleod, QC, of the Faculty of Advocates, and Ann Ritchie, president of the Glasgow Bar Association, are among those due to give evidence to the Justice Committee examining the Bill.
The proposal has been met with widespread opposition in legal circles, with opponents arguing the requirement is a central element of Scots law and an important safeguard against miscarriages of justice.
Earlier this year, only 3% of 528 lawyers polled for Scottish Legal News felt the move would "strengthen and improve" Scottish justice.
But last week Justice Secretary Kenny MacAskill said the system was being "failed" by the need for corroboration, which blocked rape and domestic abuse cases reaching court.
"Corroboration in our legal system is a barrier to obtaining justice for the victims of crime committed in private or where no-one else was there," Mr MacAskill told Parliament.
"In a modern society, it is not acceptable for victims to be left to suffer in silence, for justice not to be delivered."
He said safeguards to prevent miscarriages of justice would be included in the Bill, with greater emphasis placed on overall quality of evidence, and said jury majorities would be raised from a majority to two-thirds, meaning 10 out of 15 jurors must find the accused guilty to secure conviction.