CITY FIRM Norton Rose is campaigning for a client who is in dispute with the Inland Revenue over an arrangement to reduce inheritance tax.
The firm made the arrangement in 1989 for the freehold of Lady Ingram's property to be transferred to her children before she died, but for her to remain in the house as a tenant.
In May the High Court backed the arrangement. But the Inland Revenue has just appealed against the decision and the case may go before the House of Lords.
An Inland Revenue spokesman said: "We believe that because Lady Ingram was living in the house at the time of her death, it remains part of her estate, all of which is subject to inheritance tax."
Norton Rose partner Michael Macfadyen is now planning a fighting fund for Lady Ingram's family.
He said tax bills would not be high enough in all cases to make it worthwhile for individuals to take the taxman to court but the Ingram case could provide a focal point for those similarly affected.
"If the funds are not raised, the High Court decision would be reversed by default. That will throw the law into a state of uncertainty," he said.
Lady Ingram's daughter Ann Peck said: "It was my mother's overriding wish that her childhood home should remain in our family and not be sold because of death duties. There must be many other families in the same position as us."
Law and accountancy firms are being asked to contribute £500 for each client who may be affected by the case. Lawyers involved in the case are keeping their fees to a minimum.