Discrimination against gay, lesbian and bisexual workers is currently under-reported, according to the Equality Authority.
Its chief executive, Mr Niall Crowley, said only 3.5 per cent of the authority's case files under the Employment Equality Act last year related to the sexual orientation ground.
No such case had yet come to a conclusion before the Equality Tribunal, he added.
The authority believed such cases were under-reported because people feared exposure and believed their experiences would not be taken seriously.
However, its 2002 case files identified a wide spread of issues including claims of harassment, less favourable treatment, discriminatory dismissal and discrimination at the point of recruitment.
Mr Crowley was speaking at the launch in Dublin by the Irish Congress of Trade Unions of guidelines for union negotiators on lesbian, gay and bisexual rights in the workplace.
The guidelines urge union activists to recognise that discrimination on sexual orientation grounds is a trade union issue.
"Discrimination leads to isolation, abuse and the victimisation of lesbian, gay and bisexual workers," they state.
"Unions need to negotiate policies and procedures that counteract remaining discrimination and prejudice in all its forms against lesbian, gay and bisexual workers."
Ms Aileen Morrissey of the Mandate trade union outlined a recent case which highlighted the extent of the problem in some workplaces.
A barman, who was a member of the union and had no problem stating that he was gay, had been suspended by his employer after being asked if, being "the type he was", he would be the type to "put his hand in the till".
When the union intervened his employer said he could not remember why he had suspended the barman and reinstated him.
Within a week, however, his working environment had become so bad he had been forced to take sick leave and shortly afterwards, he was sacked.
The barman successfully challenged his dismissal and was awarded compensation, "but now he has no work, and this man did nothing wrong", Ms Morrissey said. This raised the question of whether the existing penalties were enough to prevent such discrimination. "I think not," she said.
Mr Chris Robson of IMPACT urged unions not only to take the ICTU guidelines on board but to actively promote them and inform members that they were union policy.
