Women driving "goes against the laws of modesty within our society", it said.
A spokesman from the Belz Community said they were "saddened" by the "misrepresentation" of the notice.
The Home Office said it would be inappropriate to comment on individual cases, adding that the government "believes everyone in this country is equal and everybody is free to lead their lives as they see fit".
The Belz, who originated in Ukraine in the early 19th Century, are an ultra-Orthodox sect who follow Haredi Judaism.
The letter, which was signed from the "spiritual management" of Belz institutions, said: "There has been an increase in incidences of mothers of our students who have begun driving cars, something that goes against the laws of modesty within our society."
This had led to "a lot of exasperation among other parents", it said.
The group's leader in Israel, Rabbi Yissachar Dov Rokeach, had advised that "if a woman is driving a car, she cannot send her children to be educated in Belz institutions", it said.
It added that women with a "specific reason" to drive could submit a request to a special committee.
Orthodox Jewish women driving ban unacceptable, says Nicky Morgan - BBC News