Labour has sacked three shadow ministers who joined dozens of their colleagues in defying the party to back a Queen's Speech amendment calling for Britain to remain in the single market and customs union.
Andy Slaughter, Ruth Cadbury and Catherine West were all dismissed while a fourth, Daniel Zeichner, resigned as splits were revealed within Jeremy Corbyn's party following the leader's call for MPs to abstain.
Some 49 Labour MPs joined a group including the SNP and Liberal Democrats in voting in support of the amendment tabled by former shadow cabinet minister Chuka Umunna.
A total number of 101 MPs backed the amendment against 322 against.
Mr Zeichner, who resigned just before the vote, later said the crackdown on disloyalty actually showed Mr Corbyn was ready to take his party back into power.
"In the past people with my views have been tolerated, but today it was very clear that any diversion from the published line would not be tolerated," he said.
By voting the rebels defied the Labour leader, who has committed to ending free movement of EU citizens and leaving the single market.
His party had campaigned on a promise to attempt to retain the "exact same benefits" of the trade bloc in Brexit negotiations.
The Brexit-related vote came after the government fought off a Labour amendment calling for an end to austerity by 323 votes to 297 and before a final vote in favour of the Queen's Speech, which was approved by 323 votes to 309.
Mr Corbyn said the main vote showed the Conservatives "survived by the skin of their teeth today, supported by the DUP, but this is a government in chaos" as he pledged to oppose its legislative agenda "every step of the way".
Labour MP Stella Creasy earlier withdrew her Queen's Speech amendment after it brought about a change in abortions for Northern Irish women.
Chancellor Philip Hammond confirmed women from Northern Ireland will be able get abortions for free on the NHS in England.
The government faced a possible defeat on the issue after Ms Creasy's amendment gained cross-party support from more than 50 MPs.
Instead the later amendment brought headaches for the Labour leadership as Tories said the vote showed the leading opposition was in "total chaos" over Brexit.
Conservative MP James Cleverly MP said the "deep division" would lead to Britain getting "the worst Brexit deal at the highest price".
Lib Dem leader Tim Farron said voters would feel "utterly betrayed" that Mr Corbyn had "failed to oppose this government's extreme Brexit agenda".
Mr Umunna had called on the government to "get real" over Brexit, warning Britain would not be able to take on big business if it only had access to the trading bloc, rather than being a full member.
"Large, multi-national companies work across borders to maximise their profits and reduce these protections," Mr Umunna said.
"One national government cannot take on the power of these people alone."
Business Secretary Greg Clark accused Mr Umunna of political amnesia as he closed the Queen's Speech debate.
"(Mr Umunna) wants a good deal from Brexit with a parliamentary vote that involves transitional arrangements, respects the devolved administrations, and protects rights - so do I," he told MPs.
"But when he adds to that this membership of the single market does he not recall that only three weeks ago he was running on a programme promising to leave it?
"That's quite a big thing to forget, Mr Speaker, a bit like forgetting that he hasn't got confidence in the Leader of the Opposition."