Britain's main opposition Labour Party says the court ruling demanding parliamentary approval for the start of the formal divorce from the European Union underlines the need for Prime Minister Theresa May to consult lawmakers on her negotiating terms.
However, the government has taken the blow as a challenge and said to be appealing against the verdict to the Supreme Court.
The court ruling came on a landmark case brought by businesswoman Gina Miller who sought to block the Prime Minister from formally enacting the Britain's withdrawal from the European Union without first submitting it to a parliamentary vote.
May previously accused those behind the legal challenge of seeking to frustrate the Brexit process.
Meanwhile, Lisa Nandy of the Labour party said she is confident that Article 50 will be triggered and Britain will leave the bloc whether or not parliament votes on the issue.
Yet the High Court has now said that is not the case - a decision that the government is now set to appeal - perhaps ironically, to European courts.
After the High Court ruling on Thursday, Labour Leader Jeremy Corbyn called for greater transparency on the terms of Brexit.
The Parliament could block Brexit in theory especially as most of these lawmakers had supported in staying in the European Union in June. It's unclear whether that would be done with a simple motion to trigger Article 50, or would need a full Act of Parliament.
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She plans to telephone European Commission President Jean-Claude Juncker Friday to spread the word that her plan is still to start the process to remove Britain from the EU by the end of March.
David Greene, who is acting for Deir Santos, one of the applicants, says the government must accept the "the constitutional reality that Parliament must have early involvement in the process".
The decision was hailed by Brexit select committee chairman and Leeds Central MP Hilary Benn as "an important judgement on the sovereignty of Parliament".
This means the government can not start the process of leaving the European Union on its own.
He added that "the government does not have power under the crown's prerogative to give notice pursuant to article 50 for the United Kingdom to withdraw from the European Union".
Gina Miller speaks outside the High Court following its ruling on a challenge to the British government's right to start divorce proceedings from the European Union, in central London on November 3, 2016. "Before taking off, it is always a good idea for the pilot to discuss with the passengers and crew where they might want to land", he added. "The fact that they have to approve legislation also gives them an opportunity to be a lot more involved in how Brexit plays out".