Story highlights Miller won a case in November that thwarted the Prime Minister's Brexit plan

The businesswoman was sent death threats after her win

London (CNN) A 55-year-old man has been arrested over racist online threats he allegedly made against Gina Miller, the businesswoman behind a high-profile legal challenge to Brexit.

While London's Metropolitan Police did not name Miller, the businesswoman confirmed in an email to CNN that the case was related to her.

Gina Miller speaking outside the High Court in London on November 3 after winning a legal Brexit challenge.

The police said that the man was arrested on Monday on "suspicion of racially aggravated malicious communications" and that he was later released on bail.

The case is among "a number of ongoing investigations by the police into a number of serious abusive and threatening letters, emails and telephone calls," Miller said.

Miller, a 51-year-old investment banker, was the chief claimant in a case that thwarted the UK government's plans to formally begin the process of Britain's exit from the European Union without a vote in parliament. British Prime Minister Theresa May had hoped to bypass MPs to trigger Article 50 of the Lisbon Treaty -- the legal mechanism required to begin the divorce process from the union -- by the end of March.