Lib MPs up for same-sex conscience vote

A majority of Liberal MPs are ready for a conscience vote on gay marriage, a crossbench senator who is drafting a same-sex marriage bill says.

Liberal Democratic Party senator David Leyonhjelm is rushing to draft a private member's bill to legalise gay marriage and is urging Prime Minister Tony Abbott to let his colleagues vote however they want.

Senator Leyonhjelm says there is a "90 per cent certainty" they will agree to a conscience vote but unless a bill existed, the coalition party room would not consider it.

"That does not guarantee success - you still need to get a majority in both chambers to change the law," he told News Corp Australia.