The coalition says Kevin Rudd is just playing politics on gay marriage and is using the issue to distract from the fact he hasn't got any plans for jobs or the economy.
The prime minister used the first leaders' debate on Sunday to announce his Labor government would within 100 days of regaining office introduce to parliament a new bill to allow same-sex marriage.
Mr Rudd said voters wanted this change and he urged the coalition to dump its decision not to allow its MPs a conscience vote on the issue as "a mark of decency".
Opposition Leader Tony Abbott said it was an important issue but the coalition's immediate priority was the cost of living and jobs.
He reiterated that position on Melbourne radio on Monday.
"It's a very important issue. It's not the only issue though," Mr Abbott told Gold 104 FM.
The coalition's campaign spokesman Mathias Cormann said Mr Rudd didn't have anything positive to say about jobs or the economy, so was "casting around for distractions".
"Kevin Rudd is just playing politics with this," Senator Cormann told ABC Radio on Monday.
"He knows that it is unlikely there would be a majority for gay marriage in the next parliament, given it has been so comprehensively defeated in this parliament."