Fred Nile has pulled his crucial support for state government legislation after Premier Barry O'Farrell's public comments in favour of same-sex marriage.

In a letter sent to Mr O'Farrell on Monday night, the Reverend Nile said he was "very upset at the Premier's public support for homosexual marriage and his challenge to Tony Abbott's rejection of a Conscience Vote on the Homosexual Marriage Bill".

Fred Nile is upset that Barry O'Farrell has come out in support of same-sex marriage. Credit:Peter Rae

“Our Christian Democratic Party will withdraw its support for O'Farrell legislation until his challenges to Tony Abbott's policy cease."

The Premier last week said he had changed his mind on the issue and now believes that same-sex marriage should be given legal status under the federal Marriage Act.