At least two government members have promised to vote against the issue although the bill's passage through the lower house of parliament is guaranteed.
It will face greater opposition in the Senate next week, where at least one government Senator has indicated she will oppose the move.
Opposition Immigration spokesman, Tony Burke, is urging Coalition members to vote against the bill saying it will cause pain to some of the most desperate people in the world.
“We should oppose this bill because of what it does, because of the motivation that brought it here and because, regardless of any amendments the government might seek to move this bill is itself irredeemable,” Mr Burke said.
The Prime Minister, John Howard, has refusing to take part in a slanging match between his backbenchers over the government's controversial migration bill.
Mr Howard said he would not be expressing any opinions outside parliament.
He stressed a lot of changes have been made to the bill taking into account the concerns of some colleagues.
But in the end the overwhelming majority view must be respected he said.
Mr Howard says the public wants strong border protection legislation and that is the rationale behind the bill.
Liberal moderates are worried the laws will dismantle a key concession they won from the government last year which ensured that women and children would not be held in immigration detention.
Backbenchers Petro Georgiou and Russel Broadbent reportedly intend to cross the floor to vote down the legislation.
Mr Howard has urged unhappy MPs to abstain rather than side with the opposition.
Queensland Liberal MP Cameron Thompson has branded his colleagues' position as unprincipled.
West Australian Liberal Don Randall says dissident MPs will embarrass themselves not the government by voting against the bill.