Nearly two-thirds of retail workers are earning less than €451 per week.
That is according to a new report published by the trade union Mandate, which is warning of a lack of available hours for workers.
The union is calling for a legislative change to allow workers to work more than their 'banded-hours' contracts where extra working hours become available.
Jonathan Hogan, Assistant General Secretary with Mandate, told Newstalk Breakfast there are several shortfalls.
"Compounded even further, in terms of earning levels, is the fact that people don't get access to full-time jobs," he said.
"They don't get access to available hours when they become available in the various locations.
"This was to improve by the introduction of the Employment (Miscellaneous Provisions) Act in 2018, which gave rise to bands of hours.
What we're seeing now is … even though 40% of our members, through that survey, want more hours they can't access more hours."
'Losing a lot of people'
When it was put to him that if some people are given more hours, others would be laid off, Mr Hogan said there is a shortage of staff at the moment.
"That won't stack up post-COVID," he said.
"Our experience on the ground dealing with major national retailers is... they can't attract new starters into the business because of the packages they're offering and they can't retain people.
"So, they're losing a lot of people now to the public service."
He said there are hours to be filled which are not being offered.
"There's an availability of hours there that's not being given, not being offered to current staff," he said.
"We do accept that a business has to be run and people have to service that business at different times of the day [but] you have 40% saying that they're prepared to do that.
"The shortfall is, our members want access to more hours... there's less people working in the shops now than ever before because of the migration out of retail.
"They don't see it as an attractive job - what we're trying to do is change that.
"What this research has found is people aren't given access to decent jobs and decent hours," he added.
Listen back to the full interview below: