Jeremy Corbyn will order Labour MPs to vote to trigger Brexit if parliament gets a say in the matter, despite objections from some of his own Remain-supporting MPs.
The Labour leader said his party must vote to begin the formal process of Britain leaving the EU, following last summer's referendum on membership.
"It's very clear – the referendum made a decision that Britain is to leave the European Union," he told Sky News. "It wasn't to destroy jobs or living standards or communities, but it was to leave the European Union and have a different relationship in the future."
The government is expected to lose next week's Supreme Court case on whether it has to consult MPs before beginning the formal Brexit process, meaning parliament is likely to be given a vote on the formal process of leaving the EU within the next few weeks.
"I've made it very clear the Labour Party accepts and respects the decision on British people," said Corbyn. "We will not block Article 50."
Asked whether that would mean a three-line whip was imposed on Labour MPs – formally requiring them to back Brexit – Corbyn insisted: "It means all Labour MPs will be asked to vote in that direction next week, or whenever the vote comes up."
A spokesperson for the Labour leader told BuzzFeed News they did not comment on whipping procedures.
While the overwhelmingly majority of Labour members campaigned for Remain there were substantial Leave votes in many constituencies held by the party. Corbyn, who has a long history of Euroscepticism, is now dealing with the challenge of placating a pro-EU activist base while trying to win over potential Labour voters in marginal constituencies who backed Leave.
However, the decision to endorse the referendum result has left some Labour MPs in Remain-voting seats fearful that their seats could be under threat if they anger constituents by voting for Brexit.
Liberal Democrat leader Tim Farron, who has positioned his party as an overtly pro-EU campaign, criticised Corbyn's decision: "Labour’s claim to be the official opposition must break the Trade Descriptions Act. It comes after Labour claimed to have stopped hard Brexit the same day that Theresa May announced she would take us out of the single market – and I thought that was beyond parody."