David Cameron is to avoid a showdown with his own backbenchers by ordering Conservative ministers to abstain in a key vote over deporting foreign criminals.
An amendment to the Immigration Bill tabled by Tory backbencher Dominic Raab would prevent foreign nationals dodging deportation after serving a jail sentence by claiming that it would breach their right to a family life.
Downing Street said Mr Cameron had "a very great deal of sympathy" with Mr Raab's intentions but feared that his proposals might not be workable, as they could trigger a large number of appeals to the courts.
The prospects of the measure being passed in the Commons this afternoon dwindled dramatically after Labour signalled it would join the Liberal Democrats in voting against.
The Esher and Walton MP's proposal, supported by dozens of Tory backbenchers, would give the Home Secretary rather than judges the final say over whether deportation would breach the human rights of foreign criminals.
Mr Raab admitted there was a "risk" that the Government would face action from the European Court of Human Rights, but insisted the measure should not breach the rules because of allowances for exceptional circumstances.
But he told BBC Radio 4's Today programme: "I'm not trying to get into the totemics of Europe or pull out of Europe or scrap the Human Rights Act.
"I'm just trying to fix a problem."
A Liberal Democrat spokesman said all the party's MPs and ministers would vote against the Raab amendment because it would be "both illegal and counter-productive".
"The advice from law officers is that it is illegal," the spokesman said.
"The advice the Home Office have provided is that the effect of Mr Raab's amendment would be to make the number of deportations go down, not up, because they would be dragged through ever more legal challenges."
Alongside Mr Raab's plan, around 40 Conservatives are expected to support an amendment tabled by Nigel Mills which calls on the Government to reinstate restrictions on migrants from Romania and Bulgaria working in Britain until the end of 2018.
The amendment has been selected by Mr Bercow in the second group for debate, meaning there is unlikely to be time for it to go to a vote in the single day allotted for the report and third reading stage of the Bill.
Much of the day's debate will be taken up by dozens of technical amendments tabled by Home Secretary Theresa May in what some Tory MPs view as an effort to stifle dissent.
Mrs May has tried to appease potential rebels by unveiling proposals that would mean terror suspects can be stripped of British citizenship even if it leaves them stateless.
Opening the debate in the Commons chamber, she told MPs that the Government would not have a "blank cheque" to invoke the power and that home secretaries would be able to render someone stateless only in "very, very specific and limited circumstances".
Her amendment to the Bill stated that only naturalised citizens could have their citizenship removed and only if the Home Secretary was satisfied that it would be for the public good and if the person's conduct has seriously harmed Britain's vital interests.
The Home Secretary already has the power to take away British citizenship from those with dual nationality.
Human rights campaigners have branded the move an "alarming development" which gives the minister power to "tear up people's passports without any need for... due process".
But Deputy Prime Minister Nick Clegg told LBC radio it was " controversial but... justifiable" and would be used only "in a very, very, very small number of cases (where) people have taken up British citizenship but pose a real, real threat to the security of this country".
One of the highest-profile cases involving statelessness concerns Hilal al-Jedda, who fled from Iraq to the UK in 1992 as a refugee from Saddam Hussein's regime.
He won asylum and in 2000 was granted British nationality.
He returned to Iraq in 2004 where he came under suspicion of involvement in terrorism and in 2007 was stripped of his British nationality.
Al-Jedda, who now lives in Turkey, has since been fighting the move through a series of legal appeals.
Last October, Supreme Court judges ruled that it was illegal to make him stateless.
Despite this ruling, the Home Secretary stripped al-Jedda of his UK citizenship for a second time last month.
Labour sources confirmed its MPs would be whipped to vote against Mr Raab's amendment.
They highlighted concerns the change would be "illegal and counterproductive", and said the Opposition would bring forward its own proposals to facilitate deportation later.
Shadow immigration minister David Hanson was also highly critical of Mrs May's last-minute proposal on the removal of citizenship.
"This is no way to make policy on such a serious issue," he told the Commons.
"Facing two rebellions, the Tories pull out a policy - power to make an individual stateless - that hasn't been consulted upon, debated or considered - in fact the Home Secretary has never even mentioned it before now - in the hope it takes attention away from her rebellious backbenches.
"Exceptional powers need to be justified and need proper safeguards.
"The Home Secretary has to explain whether this change could risk making it harder to deport people, potentially bringing about lengthy legal battles with no stated objective, or being abused.
"She also needs to explain what will happen to a stateless person.
"We are proposing additional safeguards, but this measure needs much more scrutiny."