MSP Murdo Fraser is urging the Scottish Government to put a stop to plans to reform gender recognition laws.
A consultation on changes to the Gender Recognition Act 2004, due to close this week, has been seeking public opinion on plans to make it easier for people to legally change their gender.
Proposed reforms to the law include removing the requirement for medical evidence and reducing the length of time people need to live in their chosen gender from two years to three months.
The Scottish Government is also considering lowering the age limit for changing genders from 18 to 16.
The proposals have alarmed women's groups while also exposing divisions within the Scottish National Party.
Writing in The Scotsman, Conservative MSP for Mid Scotland and Fife, Murdo Fraser raised concerns about the implications for women-only spaces and questioned whether the outcome of the consultation was a foregone conclusion.
"Despite these concerns, Scottish ministers seem determined to press ahead with reform, with the responsible Cabinet Secretary, Shirley-Anne Somerville, indicating in a recent media interview that the Government was still committed to legislation in this area," he wrote.
"Astonishingly, this comment was made whilst the consultation is still open for responses, suggesting that it is little more than a sham exercise."
He went on to say that there was "no scientific evidence whatsoever to support the belief that a child is born into the wrong body", and suggested that the Children's Commissioner and Scottish Human Rights Commission have failed to act because they are "terrified" of being labelled transphobic.
He was also critical of allowing young people to embark on medical gender reassignment treatment involving puberty blockers, hormone treatment and possibly irreversible surgery, warning that the long-term health effects were still unknown.
"Many children reporting with gender dysphoria have a variety of serious and complex problems, including mental health issues, but the default response to any child reporting with gender dysphoria is to pursue an 'affirmative agenda', in other words to push them down the route of transition, without questioning the underlying causes for their condition," he said.
He quoted Sinead Watson, a young woman living with sex change regret, who claims she was "obsessively and sychophantically affirmed" by medical professionals in being transgender, as he called on the Scottish Government to halt changes to the current law.
"It seems that in this area we have abandoned evidence-based, scientific policymaking in favour of a fashionable ideology, and as a result we risk doing irreparable harm to the lives of hundreds of children," he said.
