Labour will not "frustrate" the process for invoking Article 50, Jeremy Corbyn said after the Supreme Court ruled Parliament must give permission to start the formal Brexit process.
But the Labour leader said his party would seek to amend the legislation the Government has been forced to produce in order to prevent Theresa May allowing the UK to become a "bargain basement tax haven".
Government loses Brexit Supreme Court battle over power to trigger Article 50
He said: "Labour respects the result of the referendum and the will of the British people and will not frustrate the process for invoking Article 50.
"However, Labour will seek to amend the Article 50 Bill to prevent the Conservatives using Brexit to turn Britain into a bargain basement tax haven off the coast of Europe.
"Labour will seek to build in the principles of full, tariff-free access to the single market and maintenance of workers' rights and social and environmental protections.
"Labour is demanding a plan from the Government to ensure it is accountable to Parliament throughout the negotiations and a meaningful vote to ensure the final deal is given Parliamentary approval."
Green Party co-leader Caroline Lucas confirmed she would vote against triggering Article 50 on the timetable set out by the Prime Minister.
Mrs May has vowed to trigger Article 50, starting the formal two-year countdown to Brexit, by the end of March.
Ms Lucas said: "This case is a win for parliamentary democracy, and a blow for those ministers who planned to railroad Brexit through without any proper scrutiny.
"The spotlight now falls on MPs - and in particular the Labour Party - to properly scrutinise the Government's plans and act accordingly.
"That must mean that Labour rethink the support they've given to triggering Article 50 prematurely, and instead join those of us who refuse to be pushed into Theresa May's artificial Brexit timetable."
She added: "I will not be capitulating to the Tories over Brexit - and will vote against prematurely triggering Article 50 in the spring."