Unlike some, the Labour leadership has never advocated seeking to overturn the Leave vote. But in his speech this morning, John McDonnell went a step further. "It is time we were all more positive about Brexit," the shadow chancellor said. "Labour wants to see an ambitious Brexit Britain." McDonnell also confirmed that the party would not push for a second referendum and would vote to trigger Article 50 if required. To do otherwise, he warned, would "put us against the majority will of the British people and on the side of certain corporate elites".

But Labour policy, as McDonnell and Jeremy Corbyn have often noted, is made collectively, not indvidually. Back in September, the party's conference passed a motion which kept open the option of remaining. It read: "[Conference] recognises that many of those who voted to leave the EU were expressing dissatisfaction with EU or national policy and were voting for change, but believes that unless the final settlement proves to be acceptable then the option of retaining EU membership should be retained,” the motion says.

"The final settlement should therefore be subject to approval, through Parliament and potentially through a general election or a referendum."

But Labour's National Executive Committee subsequently stated that the motion was passed due to an error in compositing and was not party policy. "Conference policy on Brexit has been misinterpreted in some reports as committing Labour to a second referendum on UK membership for the EU, so for the avoidance of doubt we want to make clear that it is not our policy.

"We have called for the government to be transparent and inclusive in their process and to respect rights at work and other protections that the EU provided. Those issues will be our focus in holding the Tory government to account."

Party activists, however, still hoped to shape the party's Brexit policy at this weekend's National Policy Forum meeting (the first in two years). Some are now accusing McDonnell of pre-empting this process. Delegate Emma Burnell tweeted: "Can anyone tell me the point of the NPF discussing Brexit this weekend if McDonnell has just announced our (dreadful) response today? Precisely why should I waste my time and train fare to go to the NPF if they treat us like this?"

When asked what Labour's official stance was, a spokesman said: "Our support for invoking Article 50 is unconditional but we would seek to amend or influence the government's negotiating terms in line with our priorities."