A grandmother, adopted more than 50 years ago, has taken her battle to find out information about her past to the High Court.

Linda Gunn-Russo's is challenging a decision by the Nugent Care Society, which was involved in her adoption, to deny her access to records, and also the Health Secretary's subsequent refusal last year to intervene in the case.

Her case, which is backed by the human rights pressure group Liberty, raises issues of general importance for adopted children and their "right to know" their past.

Mr Justice Scott Baker, sitting in London, heard that Ms Gunn-Russo, 54, of Crosby, Liverpool, had been allowed to see some information but it was insufficient to allow her to complete the jigsaw of her personal history.

Her counsel, Thomas de la Mare, said the adoption society had "fundamentally misunderstood the law of confidence and adopted inflexible rules" when it refused Ms Gunn-Russo access to files on her natural parents and adoptive family, Thomas and Kathleen Rogan.

She is also claiming it breached of her rights under the 1998 Human Rights Act.

Outside court, Ms Gunn-Russo, a member of Trace, the Transatlantic Children's Enterprise, which helps children find their American GI fathers, said she hoped her legal battle would help others in similar searches.

"I want to open the floodgates for other people so they have freedom of information which will enable them to know how they got to where they are today," she said.

She was adopted in 1948 at the age of two and managed to trace her birth mother, Elizabeth Gunn, in 1976, visiting her frequently until she died in 1989.

Her mother was a nurse with the US Red Cross when she fell in love with Mid Russo, an American GI based in England just after the Second World War. He died before she could trace him. But Ms Gunn-Russo has maintained a relationship with her half-sister Joyce Russo.

In court, Mr de la Mare accused the Nugent Care Society of "impermissibly fettering its discretion" under the 1983 Adoption Agencies Regulations and of having an inflexible policy of refusing adoptees access to files, irrespective of the circumstances of individual cases.

The Nugent Care Society's justification for not releasing information was that it had been obtained in confidence from potential adopters and the birth parents and in no circumstances could that information be disclosed.

The hearing continues.