Brexit will go down in history as a "national failure" if Theresa May fails to protect jobs and living standards in the UK, Jeremy Corbyn warned on Wednesday (29 March).
The Labour leader's statement came just hours before Sir Tim Barrow, the UK's chief representative to the EU, hand-delivers the Article 50 notification to the EU Council.
The move will start the two-year-long divorce talks with Brussels, with May planning to call for UK-wide unity as she addresses MPs after Prime Minister's Questions (PMQs).
"The British people made the decision to leave the European Union and Labour respects that decision. Britain is going to change as a result. The question is how," Corbyn said.
"The Conservatives want to use Brexit to turn our country into a low-wage tax haven. Labour is determined to ensure we can rebuild and transform Britain, so no one and no community is left behind. It will be a national failure of historic proportions if the prime minister comes back from Brussels without having secured protection for jobs and living standard.
"That's why Labour has set the clear priorities of full access to the European market, rights at work and environment protection. And we will hold the government to account every step of the way."
But despite Labour's call for full access to the EU's single market, May said in her Lancaster House speech that she would not seek to maintain the UK's membership of the market.
The UK government also wants a bespoke customs agreement with Brussels so that Britain can broker its own free trade deals.