The law currently requires anyone wishing to change the gender on their birth certificate to undergo gender reassignment surgery.
"If passed, the bill will give applicants the right to choose their birth certificate gender as male, female or another non-binary option," Mr Walsh said.
"What this legislation enables people to do is change their gender on their birth certificate whether they've gone through that process or not."
Mr Walsh said the Nationals opposition is unlikely to have any impact on today's debate.
"The Government in the lower house has the numbers for it to pass through, and then the debate will happen in the upper house in a few weeks time where this is a number of cross-benchers," he said.
"It will effectively come down to where those cross-benchers decide to vote as to whether the legislation is passed or not."
Mr Walsh said his views reflected those of the people he has represented.
"This Bill has generated the most number of email inquiries coming in to my office about 'Please oppose this Bill' than any other legislation has in recent times.
"They see the proposed changes as having little regard for the silent majority who choose to live their lives identifying as the gender to which they were born.
"I think people have similar views - people believe that a birth certificate should be a document that reflects someone's gender when they are born.
"Those men and women seek legally safe and comfortable access to their own spaces and privacy in a broad range of social, living and sporting environments."
Mr Walsh acknowledged the rights of individuals to live their lives according to their identified gender, but this bill leaves far too many questions unanswered.