The Australian Christian Lobby has rejected the idea that it is 'homophobic' for people who believe that marriage should be between a man and a woman to say so publicly.

Opposition Leader BIll Shorten said in an online debate on Friday night that he didn't want to give 'haters' a chance to make life harder for LGBTI people by holding a plebiscite on the issue of same-sex marriage.

Managing director Lyle Shelton said that Mr Shorten was insulting the intelligence of millions of Australians by claiming holding a plebiscite on the issue of same-sex marriage would unleash 'homophobia'. He said it was "unbecoming" of a man seeking to be Prime Minister to "effectively bully his fellow Australians into silence by labelling them 'homophobes'".

"There are big consequences to changing the definition of marriage that have nothing to do with homophobia," he said in a statement released on the weekend. "We should be allowed to debate these consequences without emotional blackmail being used to silence debate."

Mr Shelton, who described the 2nd July poll as the "most important election in a generation", said that while the ACL "has always engaged this debate respectfully", Mr Shorten was seeking to close down the debate by "slurring people of goodwill who simply want to have a say about the most basic unit of society."

Mr Shorten has said the Australian Labor Party would introduce a bill on same-sex marriage within 100 days if elected to government while the Coalition, led by Prime Minister Malcolm Turnbull, has pledged to hold a plebiscite on the issue before any legislation is introduced.

Meanwhile, the ACL has also called on the ALP to be "clear" on whether it will support the use of Medicare funding for sex-change operations on minors.

The organisation claims the controversial Safe Schools program tells minors that they need not hold back from undergoing sex-change surgery if that's what they feel like at the time.

"The Labor Party must be clear as to whether or not they...endorse using Medicare funding to pay for sex change operations on vulnerable and impressionable minors," said Wendy Francis, the ACL's children's spokesperson.