A major recruitment drive aimed at young people in particular will be sought at the national conference next week of SIPTU, the State's biggest union.
Motions to be debated at the conference in Galway reflect a growing concern among trade unionists in general about membership levels in the private sector.
While unions have been growing in terms of actual membership numbers, the percentage of private sector employees in unions has dropped to below 30 per cent.
This is down from about 40 per cent at the end of the 1980s.
A conference motion from the Newry branch says SIPTU should build on the regrowth of political activism among young people, ignited by the recent campaign against the war in Iraq.
"The large number of young people in the service industries, finance and IT sectors in Britain and Ireland are not being recruited and are largely ignorant of the need to join, and the benefits of being a member of a trade union," the motion adds.
"Conference urges the national executive council to initiate appropriate action and strike while the iron is hot or face inevitable and severe decreases in membership over the next 20 years."
Another motion, from the Shannon Industrial branch, calls on the union to engage in a campaign that includes explaining the ideals and aspirations of the trade union movement to primary and secondary school pupils.
Another, from the Sligo branch, calls on the union's executive to lobby the Government to ensure that all grant-aided enterprises be required to commit to recognising trade unions.
These and several other motions about the same issue are likely to receive a sympathetic hearing from the union's leadership. Its vice-president, Mr Jack O'Connor, and general secretary, Mr Joe O'Flynn, are both known to regard organisation of new members as a key issue for the union.
Next week's national conference will be the final such event as an officer of the union for SIPTU's president, Mr Des Geraghty, who retires from the post in October. Apart from a brief spell as an MEP in the 1990s, Mr Geraghty has been an activist with the union for more than four decades, having first become involved with the ITGWU as a shop steward at the age of 17.
He will be 60 next month and is expected to be succeeded in the top job by Mr O'Connor.
About 500 delegates and 100 guests are expected to attend the four-day conference at NUI Galway, which opens on Tuesday. SIPTU has about 220,000 members.
The conference should also provide an indication of the current mood within SIPTU towards the Government and the partnership process.
Although the latest partnership programme, Sustaining Progress, has been in place for just a few months, a number of events since it was passed have placed unions' relationship with the Government under strain.
The most notable have been moves by the Minister for Transport, Mr Brennan, to introduce competition to the Dublin bus market and the operation of the State's airports.
With talks on a new national pay round due to begin again next March, several motions calling for the issue of low pay in particular to be addressed have also been tabled.