Many non-union workers would join a trade union if their employers approved, according to a new academic study.
It finds that employer opposition and a perception that career prospects could be damaged are among the main reasons workers choose not to join unions.
The study, by UCD industrial relations lecturer John Geary, concludes that there is much "unsatisfied demand" by workers for trade union representation.
The proportion of the workforce which is unionised has steadily declined from a peak of 62 per cent in the early 1980s to about 35 per cent today.
When the public sector is excluded, the percentage of workers in unions drops to below 30 per cent.
Prof Geary, in a paper to be published shortly, said there was sufficient "pro-union sentiment" among workers for the percentage in unions to double.
The paper, Employee Voice in the Irish Workplace: Status and Prospect, draws on two nationally representative surveys, one by the Economic and Social Research Institute and the other by UCD.
Non-union workers surveyed were divided into two categories: those working in enterprises where unions were present, and those employed where there was no union activity.
In non-unionised workplaces, almost two-thirds of employees said they would join a union if they were asked and if management offered its support.
In the absence of management approval, however, only 28 per cent said they would be prepared to join.
"The propensity to unionise in non-union workplaces is striking and is especially marked in situations where management offer their support for union representation," Prof Geary said.
In unionised workplaces, only 24 per cent of non-union workers said they had ever been asked to join a union.
Of those who had deliberately chosen not to join, 79 per cent said they would vote for continued union representation for other employees at their workplace.
"In sum, while non-union members in unionised workplaces may not have seen any direct benefit for themselves in joining a union . . . they were nonetheless supportive of the principle of union organisation and would vote to ensure its continuance," Prof Geary said.
The survey findings indicated there was potential to increase "union density" - the proportion of workers in unions - to between 56 and 71 per cent, depending on the level of employer support.
The paper is included in an international study, Employee Voice in the Anglo-American World, to be published by Cornell University Press.