Last-minute changes to schedules have a knock-on effect on travel and childcare costs, leaving employees paying to work.
Almost a fifth (17%) of workers experiencing last-minute or cancelled shifts paid over £600 a year in insecurity premium costs.
Katherine Chapman, director of the Living Wage Foundation, said unreliable work is particularly difficult during the cost of living crisis.
She said: “Soaring prices have rightly shone a spotlight on pay this past year, but this research makes clear that reliable working hours are as vital to workers’ financial resilience as a real Living Wage.
“It is shocking that 3.4 million workers are facing the cost of living crisis in low paying jobs with unstable working hours, making planning a life and a budget impossible.”
More on insecure work:
Among UK shift workers, 59% have been called into work with less than a week’s notice, while 13% of this group had less than 24 hours’ notice.
A quarter (24%) have had their shifts cancelled unexpectedly. The vast majority of cancellations are not compensated properly, with 90% receiving less than their full payment, and 26% receiving no payment at all.
The study found 22% have been forced to increase their reliance on credit or debt as a result.
Health and social care workers are worst affected, with 878,000 workers in insecure jobs that are costly to their finances.
Chapman said: “The extent of low pay and insecure work in health and social work is particularly alarming. The sector holds some of the most important jobs to our society yet they are also the most precarious and poorly paid jobs in the UK labour market.”
Chapman called on employers to provide workers with secure, guaranteed hours and notice of shift patterns alongside a liveable wage.
She added: “Action is required by both employers and the government to make this a reality in health and social care but it’s an investment that will benefit care workers and their families and is vital for the sector and wider society as our need for care continues to grow.”
Jon Boys, senior labour market economist at the CIPD said insecure shift work can create an imbalanced employment relationship.
Speaking to HR magazine, he said: “There have been concerns about one-sided flexibility with shift work and this was highlighted in the Taylor review of modern work practices published in 2017.
“CIPD research suggests that work has not become less secure in recent years. This is largely driven by the low-unemployment environment.”
A CIPD study found 7.8% of people say they would like to work more hours, and 2.7% are working part-time involuntarily because they were not able to find a full-time role.
Boys said: “Employers should only use zero-hours contracts where the flexibility inherent in these types of arrangement suits both the organisation and the individual.
“Other recommendations include reasonable compensation if pre-arranged work is cancelled with little or no notice and ensuring there are comparable rates of pay for people doing the same job regardless of differences in their employment status.”