David Cameron has swerved a confrontation with rebellious Tory MPs as he was forced to rely on Labour votes to see off a revolt over immigration.
Labour accused the Prime Minister of running "scared" of his own party after he adopted a highly unusual stance to stave off a damaging defeat.
Home Secretary Theresa May warned an attempt to prevent foreign criminals using human rights law to evade deportation could be illegal.
But to save face, Mr Cameron signalled he had a "great deal of sympathy" with its intent and ordered Tory ministers to abstain, not vote against it.
It left the Government reliant on the votes of Labour and the Liberal Democrats - as the issue also split the governing coalition.
Dominic Raab's amendment - giving ministers the final say on whether deportation breached human rights - was defeated by 241 votes to 97.
Tory backers numbered 87, including two tellers, the second most significant rebellion since Mr Cameron entered Number 10 in 2010.
Shadow home secretary Yvette Cooper mocked his handling of the issue as "a complete car crash".
"I can think of no precedent for Government ministers abstaining on an amendment that they oppose because they are scared of their backbenchers.
"The Home Secretary told the House the measure was illegal and would make it harder to deport foreign criminals instead of easier.
"Yet she then refused to vote against it.
"Ministers should be doing more to deport foreign criminals, as the numbers have fallen by 13% in the last three years - and they should now come forward with legal, workable ways to do that."
More than 200 foreign criminals successfully challenge deportation on human rights grounds every year, with around 90% relying on the "right to private and family life" under Article 8 of the European Convention on Human Rights.
Mr Raab said foreign criminals were using their right to a family life as the "joker" to escape deportation.
But Mrs May, who has repeatedly criticised the courts for upholding too many such claims, said clarifying the extent of the right was the correct approach.
There were aspects of the amendment that could "weaken our ability" to deport criminals and were "incompatible" with human rights law, she said.
Ministers feared it could open the door to legal challenges.
A move to strip foreign-born terror suspects of UK citizenship - introduced late yesterday in what was seen as a bid by Mrs May to buy off rebels - was approved.
Lib Dem Business Secretary Vince Cable accused "horribly divided" Tories of undermining efforts to reassure the public over immigration.
The Commons vote was "all a bit of a mess", he said, and distracting from figures which could allay fears immigrants were taking jobs from UK workers.
"They do seem to be panicked by the Ukip phenomenon," he told ITV News in the latest of a string of direct criticisms of his coalition partner party.
"They were horribly divided and that's not good. We need to have a common approach to reassure the public.
"We should be addressing the issues up front. We know there's a lot of public anxiety and we should be reassuring the public not to panic.
"There were some very good figures out today that provide a lot of reassurance.
"We have (had) a very successful year creating jobs - 90% of those have gone to British nationals, totally contrary to what many people believe. This popular idea that people are flooding in and taking British jobs is simply not true.
"We should be explaining that."
Government advice was that the Raab proposals were "illegal and wholly impractical", he said.