A former British Transport policeman who changed to a woman has lost her sex discrimination claim against her union.

Miss Lynsay Watson, formerly Alex Horwood, of Altyre Court, Glenrothes, took the British Transport Police Federation to an industrial tribunal, claiming sex discrimination after she claimed they failed to pay for her legal action against the police, using a lawyer of her choice specialising in transsexual cases.

She also accused them of ''pure obstinacy'' in refusing to use her new name when communicating with her, continuing to call her Alex Horwood instead. She wanted compensation for injury to feelings and her legal fees but the Edinburgh tribunal rejected her case.

She has since been dismissed and plans to take her former employers to another tribunal, claiming unfair dismissal and sex discrimination.

At the hearing against the federation, she claimed British Transport Police tried to ban her from taking hormones as part of her treatment and told her she would be reported to the procurator fiscal if she arrived for work as a woman.

She started as a police constable at Kirkcaldy in 1989 but, seven years later, informed management she was to undergo a ''gender reassignment operation'' and needed permission to assume a female role. This was refused.

She was told she had to resume duty as a ''uniform constable wearing the uniform appropriate to your male gender'' and until further notice she was to ''adopt the dress and appearance of your male gender.''

She said she was transferred to Edinburgh because colleagues did not want to work with her and she received a letter saying she should notify the force and provide doctors' certificates if her gender was being changed permanently.

She was suspended in November 1996, after she took on a female role and appearance full-time and formally changed her name, and was sacked last September. She said BTPF chairman Mike Bevan at first agreed to support her legal fight and the first bill was paid. However, this support was later withdrawn. She claimed there was a conspiracy between the federation and police management.

She said she found it quite hurtful she was still being referred to as Alex Horwood in correspondence from the federation almost a year after her change of name. She believed she was refused assistance because of the nature of her case.

Mr Bevan denied collaborating with the police. He was sympathetic when Miss Watson approached him, told her he would consider it, and gave her his home address so that she could correspond with him in complete confidence.

The tribunal said her expectations went beyond what would have been the expectations of a reasonable trade union member and she was not unfavourably treated.