A woman who worked for her parents for 20 years plans to contest their will after she was written out of it.
Dr Christine Gill is now set to challenge the legacy under the 1975 Inheritance Act after her parents' £1.5m estate was left to the RSPCA instead of her.
The 57-year-old, who is an only child, said: "I've made overtures to the RSPCA but they have been largely ignored.
"It's extremely distressing to me that we are on the brink of seeing the farm sold."
Dr Gill and her husband moved to an adjoining property more than 20 years ago so they could help out on Potto Carr Farm, near Potto, in Northallerton.
Her father, John Gill, died in 1999 and when her mother Joyce died in August last year she said the decision to leave the farm to the charity came completely "out of the blue".
Dr Gill has until October 15 to issue proceedings.
A spokeswoman for the RSPCA confirmed it has been left Joyce Gill's entire estate, and said: "The charity is unable to comment on the details of the case, but hopes that it can be resolved without the need for legal proceedings."
Adam Draper, a lawyer in Irwin Mitchell's Wills and Trusts Disputes Team said:
Dr Gill will have to claim against the estate under the Inheritance (Provision for Family & Dependants) Act 1975. The purpose of the Act is to provide reasonable financial provision in circumstances in which a person does not receive anything under the will or on intestacy.
However in order to succeed in a claim under the Act Dr Gill will need to show that the estate does not make reasonable financial provision for her .
To assess this, the court will take into account Dr Gill's financial resources and needs now and in the future, also the obligations and responsibilities the deceased had towards Dr Gill, the size of the estate and other relevant matters for example any promises made by the deceased and care provided by Dr Gill.
In addition Dr Gill may be able to bring a proprietary estoppel claim. Such claims typically arise in a farming context in which children often work on the farm property for a number of years on the understanding that they will inherit on the death of their parent.
Mr Draper concluded In order to succeed in the claim Dr Gill will need to prove that her parents, by their conduct, either by express representation or a failure to disabuse Dr Gill of the misapprehension, encouraged her to believe that she would have a right over their estate and that Dr Gill acted to her detriment by working on the farm and caring for her parents in reliance of the promise.