Government sources said they expected a third reading vote today under a pact with the Opposition to pass the bills this week.

But sources close to Opposition Senate Leader Nick Minchin insisted those were not the terms of the deal, which was only to conclude the committee stage of debate by 3.45pm today.

They believed the bill would have to be sent back to the House to incorporate an excise amendment, because taxation bills must originate in the lower house, before a final Senate vote early next week.

But the Government insisted it would push for a final vote today - and some sources aligned to Opposition Leader Malcolm Turnbull agreed that was their understanding as well.

Mr Turnbull said Senator Minchin told him he would allow the bills to be voted on in the Senate by 3.45pm today.

That would mean Mr Turnbull and his Senate backers may be forced to find seven Opposition senators to vote with Labor to guillotine debate and push for a final vote.

The Government's lower house leader Anthony Albanese yesterday insisted that he expected the vote to go ahead this afternoon.

"We are sticking to the agreement that has been reached. We have a commitment with the opposition that this will be voted on by 3.45 pm," Mr Albanese said.

"We held good faith negotiations on policy substance and the process so people could have their say. We have an agreement."

But some Liberals led by Tony Abbott - who sparked yesterday's mass walkout by handing in his resignation as the Opposition's spokesman on families, housing, community services and indigenous affairs - said he believed the legislation should go to a Senate committee for examination, and that the Senate should not vote on it until next year.

To secure passage of the legislation, only seven of the 32 Liberal senators would need to vote with the Government. It is believed at least a dozen Liberal senators supported Mr Turnbull's compromise deal with the Government in Tuesday's coalition partyroom debate.

And while Mr Albanese emphasised the Government's determination to see a vote on the scheme by this afternoon, Liberal senators who oppose the legislation could still try to block it by supporting a Senate motion to defer debate or by attempting to filibuster.

But both those tactical moves could also be defeated if just six Liberal senators voted with the Government.