Scotland's first female judge has been cleared of allegations of bias stemming from her membership of a Jewish law association.

Appeal judges at the Court of Session in Edinburgh yesterday rejected claims Lady Cosgrove's impartiality when ruling on an immigration case of a Palestinian woman was compromised by being part of the International Association of Jewish Lawyers and Jurists.

It was claimed there were "legitimate grounds" for fearing the judge may have been "unconsciously or unwittingly influenced" in her decision to reject an appeal by Fatima Helow, a failed asylum seeker, in 2004.

Lord Nimmo Smith, who heard the case with Lord Kingarth and Lord Kirkwood, rejected the allegations. While he acknowledged a "fair minded and informed observer" might assume Lady Cosgrove's membership of the IAJLJ might make her sympathetic to the Israeli position, he said it would be "unduly sensitive" to conclude this would lead to a real possibility of bias on her behalf.

Lord Nimmo Smith said the high point of the case made by Ms Helow was that the judge may have been "influenced" by views expressed in association material. He said: "We see no reason to suppose any intelligent and independent-minded judge of the Court of Session - having taken the judicial oath and being well able to form her own views - would be influenced in this way."

The senior judge said the judicial oath was an important protection against actual or apparent bias and it so imbued the judge, it became his or her second nature to abide by it.

"Obviously, the judicial oath, and all that it carries with it, cannot serve as a complete guarantee of impartiality but, in our opinion, the fair-minded and informed observer, taking account of these considerations, would give it great weight," he said.

"Such an observer would also recognise the desirability of a judge's keeping in touch with the world beyond the courts and that his or her personal interests and experience may lead to membership of or involvement with external organisations."

Ms Helow's legal challenge arose after Lady Cosgrove refused her application at the Court of Session for statutory review. Her claim for asylum had been rejected the previous year. Ms Helow, who was studying in Glasgow, gave evidence she had featured in television programmes about massacres at the Sabra-Shatila refugee camps in Lebanon in 1982.

Many Palestinian refugees, including her grandmother, aunt and uncle, were killed after Lebanese Phalangist militia entered the camps. She claimed asylum and human rights protection because of her Palestinian background, sex, Muslim religion and her support of the Palestinian Liberation Organisation.

Mick Napier, chairman of the Scottish Palestine Campaign, who has supported Ms Helow's attempt to remain in the UK, said yesterday's decision "rubbed salt in the wound" of the initial decision to refuse her claim for asylum.

Asked about the allegations of bias regarding Lady Cosgrove, he said: "I'm not privy to the inner thoughts of anyone else. But...the British citizenry...know they are not dealing with a perfect system.

"The reputation of the judicial system has suffered serious knocks and I don't think this decision does anything to revise that. There will be a widespread perception there was a very strong danger of bias and nothing was done to remove that." Lady Cosgrove Hazel Aronson was the first woman to sit on the Sheriff Court Bench, in Glasgow in 1979, and became a temporary High Court and Court of Session judge in October 1992. She was appointed on a permanent basis in 1996 and became Lady Cosgrove. In 2002, she helped rewrite the law of rape by removing force as an essential part of the crime. She is the first woman to be appointed to the Inner House judges in the Court of Session, the civil equivalent of the Court of Criminal Appeal.