A businesswoman challenging the legality of Theresa May's strategy for Brexit has become the victim of "abuse, threats and insults", the High Court has been told.
Gina Miller, an investment fund manager and philanthropist living in London, is involved in what is described as one of the most important constitutional cases in generations, currently being heard at the High Court in London.
She contends the Prime Minister has no legal power to trigger Article 50 of the Lisbon Treaty to leave the European Union without the prior authorisation of Parliament.
But the high-profile action has resulted in Ms Miller, who voted Remain in the EU referendum on June 23, coming under personal attack, senior judges heard.
After several hours of making submissions on her behalf on the first day of the hearing, Lord Pannick QC told the court that his client had received further "abuse, threats and insults".
The QC asked Lord Thomas, the Lord Chief Justice, who is presiding with two other judges, to repeat public warnings given by a judge at an earlier hearing that such abuse was entirely inappropriate and in extreme cases could amount to contempt of court.
In an apparent attempt to discourage further abuse, Lord Thomas said of the hearing: "This is a point of law being taken. Although it has political consequences, the point is not a political one."
Ms Miller is the lead claimant in a historic legal action with several other applicants opposing the use of Article 50, including those from the so-called People's Challenge, which claims the backing of thousands of supporters.
Britons living in France are also intervening as Fair Deal for Expats, along with individuals from other countries living in the UK anxious to secure guarantees for their rights gained as EU citizens.
A group referred to as "the AB Parties" say they are representative of a large class of "ordinary, poor or otherwise vulnerable" people and their children whose fundamental human rights and stability are at stake.
The various parties, including the Government, are represented by a total of 11 QCs backed by junior counsel in a courtroom also packed with members of the public. Those for and against Brexit held rival demonstrations outside the High Court.
Lord Pannick argued the Government lacked legal power to use the royal prerogative to notify Article 50 and begin the process of removing statutory rights granted to UK citizens under the European Communities Act 1972, which made EU law part of UK law.
The QC said: "The issue in this case is not whether this country should remain a member of the EU, or leave the EU. The question is a much narrower, but important question.
"The question is whether the Government may take action unilaterally to notify, or whether it needs parliamentary approval to do so."
He described the notification of Article 50 as "the pulling of the trigger", and said there would be a "dramatic impact on domestic law".
Notification "deprives people of statutory rights conferred by Parliament". He submitted: "That cannot be done by Executive action."
Lord Pannick said: "Many of the rights that Ms Miller and others currently enjoy will be removed if the notification is given - for example, Ms Miller's right to free movement, her right to free movement of goods, her right to freedom of services across Europe."
Government lawyers are arguing that if Ms Miller and her supporters' legal challenge succeeds, the Government "could not give effect to the will and decision of the people, as clearly expressed in the referendum, to withdraw from the EU without further primary legislation".
Attorney General Jeremy Wright, the Government's leading law officer, is at the centre of the legal battle.
He has stated: "The country voted to leave the EU in a referendum approved by Act of Parliament.
"There must be no attempts to remain inside the EU, no attempts to rejoin it through the back door, and no second referendum.
"The result should be respected and the Government intends to do just that."
Because of the urgency and constitutional importance of the case, any appeal is expected to be heard by the Supreme Court, the highest court in the land, before the end of the year.
Asked outside court what kinds of threats she had been receiving, Ms Miller said: "Death threats - not pleasant is it?"
The first applicant to lodge a Brexit legal challenge was London hairdresser Deir Dos Santos.
Dominic Chambers QC, appearing for Mr Santos, told the court that the sovereignty of Parliament was at stake.
Mr Chambers said: "Under the doctrine of parliamentary sovereignty, no person or body is recognised by the law as having the right to override or set aside the legislation of Parliament.
"What Parliament has enacted only Parliament can take away."
The hearing continues on Monday.