Sir Keir Starmer will not face a parliamentary investigation over claims he misled MPs about the process to appoint Lord Mandelson as US ambassador.
The House of Commons voted 335 to 223 against a Conservative-led motion which sought to trigger the inquiry.
Some Labour MPs on the left of the party said the PM should have referred himself to the Privileges Committee, but the majority voted to reject the motion after a concerted operation by No 10 to ensure they were on side.
Sir Keir has denied accusations he misled MPs over whether vetting for the role of US ambassador followed "full due process" and his assertion that "no pressure whatsoever" was applied to officials at the Foreign Office.
Conservative Party leader Kemi Badenoch tabled a motion which sought to have the PM's remarks assessed by the cross-party committee responsible for looking into cases of MPs breaking parliamentary rules.
The Ministerial Code states that ministers who knowingly mislead Parliament are expected to resign, while any inadvertent error should be corrected "at the earliest opportunity".
Badenoch had suggested Labour MPs were "acting like sheep" for labelling the motion a "stunt".
But some Labour MPs questioned why they had been instructed to oppose it and suggested it risked looking similar to a "cover-up".
The division list showed 14 Labour MPs rebelled to support the motion while another voted both aye and no, which is usually regarded as a formal abstention.
It is not yet clear what action those Labour MPs who did not follow No 10's orders to oppose the motion will face.
The Lib Dems, SNP, Greens, DUP, Plaid Cymru, Reform and nine independent MPs were among those who also voted with the Tories in favour of the motion.
A total of 53 Labour MPs did not have a vote recorded - this can be because they have been given permission to miss the vote or are on government business, and does not mean they are abstaining.
South Shields MP Emma Lewell, who was among the rebels, told the debate that the government's handling of the vote "smacks, once again, of being out of touch and disconnected from the public mood".
She said: "It has played into the terrible narrative that there is something to hide and good, decent colleagues will be accused of being complicit in a cover-up."
Lewell said Sir Keir should have referred himself to the committee "with a clear statement that he is doing so to clear his name".
Speaking to the BBC's Politics Live, Labour MP Rebecca Long-Bailey suggested there would be a "moment of reckoning after the local elections" on 7 May for Sir Keir's future.
But several Labour MPs defended the government's approach during the debate, with Gurinder Singh Josan describing the call for a Privileges Committee referral "premature" given the vetting process was being scrutinised elsewhere in Parliament.
Cardiff West MP Alex Barros-Curtis said he did "not believe the case was made out" for the motion by the Conservatives.
In a sign of the government effort to ensure the motion was rejected, Labour MPs campaigning in Scotland ahead of next week's elections were summoned back to Westminster.
Opening the debate, Badenoch examined Sir Keir's defence of his remarks before noting the Ministerial Code is "very clear" in the need for the record to be corrected at the earliest opportunity.
She said: "It is very obvious that what the prime minister said at the despatch box was not correct. It's clear that full due process was not followed."
Senior cabinet minister Darren Jones accused Badenoch of "ranting incoherence" as he defended Sir Keir's handling of the issue.
Pressed by Badenoch to repeat the PM's assertion that "no pressure existed whatsoever" in the case, Jones said Sir Keir's words should be placed "in the right context".
Jones was heckled by opposition MPs as he said Sir Keir was "specifically responding to the allegation that there was pressure that Peter Mandelson should not be vetted at all and that he should be sent to Washington regardless of the vetting outcome".
Liberal Democrat leader Sir Ed Davey earlier said the country needed a government focused on dealing with cost-of-living concerns, adding: "Crucially it needs a government that it can trust."
SNP Westminster leader Stephen Flynn said Labour MPs "cannot outrun Peter Mandelson, they cannot outrun their own prime minister and his record".
Reform UK deputy leader Richard Tice said Sir Keir "prides himself on process" but anecdotally it "seems that there is a culture that does not exist around him and within him"; while Green MP Ellie Chowns said "it is clear that there is a case to answer here" for the PM.
Lord Mandelson began the Washington ambassadorial role in February 2025 but was sacked in September after Downing Street said new information about the depth of his relationship with late sex offender Jeffrey Epstein had emerged.
Sir Keir has faced repeated questions over the appointment, including on why the peer was given security clearance for the role by the Foreign Office despite concerns being raised by vetting officials.
The Commons debate on Tuesday came after the Foreign Affairs Committee heard further evidence about the vetting process, including from the senior civil servant at the Foreign Office when the PM decided to send Lord Mandelson to the US.
Sir Philip Barton said no-one in Downing Street consulted him before making the decision and also noted he thought the appointment could be a "potentially difficult issue" because of the peer's known links to Esptein.
He said he was "presented with a decision" made by Sir Keir and "told to get on with it".
And Morgan McSweeney, the PM's former chief of staff, told MPs he made "a serious mistake" in recommending the appointment of Lord Mandelson.
McSweeney said that No 10 wanted Lord Mandelson in post "quickly" but insisted officials were never asked to "skip steps".
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