Senior Tory Sir Jacob Rees-Mogg warned he is prepared to vote down Rwanda deportation plans to stop the government looking “hopeless”.
Rebels are pushing for a series of major changes to the legislation to toughen it up when it returns to the Commons on Tuesday.
But centrists have warned they will oppose any move to make the plan even stronger amid fears it will go against international law.
Rishi Sunak will continue his charm offensive over the next few days in the hope of seeing off a revolt on the flagship legislation.
Sir Jacob said passing the bill is of “huge importance” but only if the new laws will be effective.
“Passing an ineffective bill would make the government look hopeless,” he told GB News.”
“In many ways, it would be better to do nothing than to fail again, because this is actually the third go at trying to get people deported to Rwanda.”
Former prime minister Liz Truss said: “We need to crack down on illegal migration and remove the loopholes being exploited by activist lawyers.”
“It’s essential the legislation we are passing is watertight. That’s why I am backing amendments to the Bill.”
The Prime Minister hopes the Safety of Rwanda Bill will revive his stalled deportation plan by blocking legal challenges made on the claim that Rwanda is unsafe.
It would allow ministers to disapply the Human Rights Act but does not go as far as overriding the European Convention on Human Rights.
Former justice secretary Sir Robert Buckland has put forward three changes to water down the bill by allowing human rights laws to still be used to challenge cases.
A leading figure in the centrist One Nation group of MPs, he claimed the bill is “unnecessarily inviting damage” by including too many legal issues that could be pursued through the courts.
The Rwandan government has said it will pull out of the scheme if it does not comply with international obligations.
Mr Sunak headed off rebels when the bill was introduced in parliament last year, securing a comfortable majority of 44.
As few as 29 Tories voting against the legislation in its final Commons stages next week could lead to a defeat.
More than that have backed the rebel amendments from the right of the party, although some of those are planning to support the government in the key vote that would send the bill on to the Lords.
A Downing Street spokeswoman said the government will be “looking at the detail” of the amendments submitted by MPs and “continuing our engagement with parliamentarians”.
She added the government does not want to do anything that would “collapse the partnership” with Rwanda or jeopardise the “efficacy” of the bill.
