Respondents on average earn £8.97 per hour – around 15% below the current minimum wage, which rose to £10.42 in April.
More than three-quarters (76%) of gig workers also experienced work-related insecurity and anxiety.
Julia Kermode, founder of IWORK, a support body for temporary and independent workers, said the gig economy model only works if all parties in the labour supply chain benefit.
Speaking to HR magazine, she said: “If workers are underpaid, feel insecure in their roles and suffer from anxiety as a result of working this way, then it’s exploitation.”
More about the gig economy:
The study comes as a number of employers face lawsuits over their treatment of gig workers, including an ongoing claim by more than 2000 Amazon drivers who want to be classed as employees.
The gig economy model means that workers are not classed as employees or protected by workers rights like sick pay, holiday pay and minimum wage.
Amazon unsuccessfully tried to have the claim struck out, arguing drivers are in fact working for delivery service partners, rather than Amazon itself.
Kermode said: “In recent years there has been a massive backlash from gig workers, who are understandably campaigning for rights from their engager.
“Unfortunately, this study isn’t surprising. It exposes what many of us were thinking – and what many gig workers are sadly experiencing – which is that this business model needs policing better and the workers protecting.”
The study found 28% felt they were risking their health or safety by doing gig work and 25% experienced pain on the job.
Respondents spent on average 28 hours a week undertaking gig work to bring in 60% of their total earnings.
Alex Wood, senior lecturer in HR management at the University of Bristol Business School, said the findings highlighted a need for reform in worker protections.
He said: “The findings highlight that working in the UK gig economy often entails low pay, anxiety, and stress.
“As food, fuel and housing costs keep rising, this group of workers are especially vulnerable and are urgently in need of labour protections to shield them against the huge power asymmetries that exist in the sector.”