The civil unions bill could morph into a relationships registry under an LNP government in a left-field move a top lawyer believes is being seriously considered.

LNP leader Campbell Newman has refused to say exactly what he will do with the civil unions bill introduced last year if he wins government on Saturday.

Uncertainty surrounds what will happen to civil unions legislation if Campbell Newman and the LNP win Saturday's election. Credit:Nicolas Walker

Mr Newman has said the LNP would like to repeal the bill, but insisted he did not want to leave couples already in civil unions in "legal limbo".

He has said he did not know if the bill could be repealed or what would happen to couples who had already entered a civil union.