The Labour leader ordered his MPs to abstain – but he was defied by the 41 who voted with the Scottish Nationalists for a suspension of “no fewer than three months”, past 29 March.
The revolt came after fresh confusion about Mr Corbyn’s stance on seeking an Article 50 extension, which would have to be agreed by all other 27 EU countries.
It left her unable to claim she has a Commons mandate for her attempt to renegotiate the Irish backstop – something the EU has refused to do so far.
Crucially, it shattered the fragile Tory truce, achieved two weeks ago when Ms May ripped up her own Brexit deal by aligning herself with the Brexiteers on the backstop.
Labour has sent out mixed messages on extending Article 50, refusing to do the running – although Emily Thornberry, the shadow foreign secretary, said the party backed it last week.
Mr Corbyn himself has declined to call for an extension and it was unclear whether Ms Thornberry was speaking with his full support, in his absence from prime minister’s questions.
The motion said called on the government to “immediately begin negotiations with the European Council to extend the period specified under Article 50(3) of the Treaty on European Union by no fewer than three months from 29 March 2019”.
Among them were leading pro-EU Labour figures including Ben Bradshaw, Stella Creasy, David Lammy, Chris Leslie, Angela Smith, Owen Smith and Chuka Umunna.
Ms May’s official spokesman said last week: “The very clear position of the prime minister is that there will not be an extension of Article 50.”
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