Mandate has said that around a third of its members are finding it difficult to feed and clothe their families.
The union represents 45,000 workers in the retail trade.
The finding was contained in research carried out by it, which looked at the effects the recession is having on its members.
Mandate said three quarters of its members are now finding it more difficult to cope in general and suffer much more stress than a few years ago.
Four in ten of its members are experiencing difficulty paying their mortgage or rent, while over half are struggling to pay utility bills.
More than seven in ten reported that they are now far less likely to visit a doctor because they could not afford the cost.
The union claims that in the past year, the average earnings of its members have been cut by around €100 a week.
Speaking on RTÉ’s News at One, General Secretary John Douglas said since the recession started, there has been a shift towards more insecure, part-time contracts in the retail trade.
He said there has been a ''systematic destruction in the quality of jobs since the recession started''.
