David Davies has urged fellow MPs to abandon reforms on gender laws.
The Conservative MP for Monmouth claimed the debate around gender and the recent consultation on the 2004 Gender Recognition Act (GRA) had been conducted without "proper consideration" and in an "atmosphere of menace".
Raising his concerns during a Westminster Hall debate, Mr Davies said that people "should not face dismissal from their jobs" for suggesting that a woman "cannot have a penis".
The government's public consultation on GRA reforms closed in October, with a response expected in the Spring.
- Read more: David Davies 'threatened with police action' for holding meetings on transgender concerns
- Read more: What is the Gender Recognition Act consultation?
Mr Davies, who has voiced his concerns around self-identification of gender in the past, said: "Before any legislation has been passed, we are already seeing organisations such as schools, hospitals and prisons allowing people to define themselves by a different gender to the one that they are born with, and in the majority of cases to which their body corresponds, and it does have an impact on others, it has an impact on the rights particularly of women to privacy and to sex-segregated spaces.
"A 15st bearded man could simply define themselves as female and there would be nothing anybody could do to object to this."
The MP told talkRADIO in October that he had been threatened with police action for holding meetings in Parliament on transgender concerns.
He has also faced accusations of being transphobic from fellow Conservative MPs, and faced backlash online for tweeting that "someone with a penis cannot be a woman".