Gina Miller, the woman who led the case against the prime minister's decision to trigger Article 50 of the Lisbon Treaty and start the UK's exit from the European Union without the prior authority of parliament, has told BuzzFeed News the judgment is "un-appealable"
She was speaking shortly before the Supreme Court confirmed it will hear the government's appeal of last week's High Court judgment on 5 December.
The court announced on Monday that 11 justices will hear the case against the judgment, which found the government could not trigger Article 50 without consent of parliament, over a three-day appeal.
Miller, the 51-year-old fund manager who was lead claimant in the case, told BuzzFeed News she was "baffled" that the government was pressing ahead with the appeal.
"I’m still baffled as to why they’re appealing, because it is actually a simple black and white letter of the law and the case is un-appealable in our view.
"It exposes more than anything that they haven’t got a plan. I think it’s a complete waste of time but say a lot about them stalling – I think it’s a stalling tactic," she said.
Miller also criticised the government for not doing enough to protect the judges who made last week's judgment from abuse and death threats, and who were called "enemies of the people" by the Daily Mail.
She said it was the role of government to "make it plain" that those "anyone who speaks up should not be targeted for hate crimes and criminal offences".
"It should have been an instant rebuttal," she said. "Rather than waiting for David Davis yesterday, Mrs May should have done this immediately before she went off to India and put a stop to it but they didn’t – and one could argue because she wants the papers on her side."
She defended the judges as "some of the greatest legal figures in our country".
"The irony is Britain is great because of its parliamentary sovereignty and the rule of law – it’s the thing around the world we’re revered for. People like Nigel Farage on the street inciting people to march on the courts is beyond disgraceful," she said.
Miller told BuzzFeed News she had received "thousands" of threats and abusive messages since the judgement.
"I did not expect the racism and the sexism and the sexual violence, I have to say." she admitted. "I thought we lived in a very different society and had moved beyond that.”
She said while she had prepared for some anger she had been surprised at the extent of the violence, which has included death threats and in one instance a campaign inciting people to “shoot me behind the ear and dump my body in a rubbish bin.”
She had been the victim of abuse on social media where it had been "like a feeding frenzy" and also on the phone and via letters sent to her and her staff.
“I’ve got a pretty thick skin, and people who know me will tell you that I really don’t care about what other people think of me,” she told BuzzFeed News.
“But what I will say is that is shows a really, really, dark side of what is happening in the UK – for people to think it’s legitimate to show this type of behaviour.”
Miller said she feared there were "too many parallels with the French revolution and 1930s Germany of where we’re going as a society, and not just in the UK but in the US, and in the far-right [movement] in Europe," she said.
The High Court ruled last Thursday that MPs should vote before the process to leave the EU is triggered, but the government has argued it should not need the consent of parliament to act.
The final decision on the appeal is expected in the New Year.