New figures from the Office for National Statistics (ONS) show that only about 58 per cent of part-time employees have a workplace pension.
Nearly nine in 10 (86.4%) employees who work full-time have a workplace pension, but that figure falls to just over half (57.8%) of those working part-time.
The figures, from 2020, also show that just over a third (34.8%) of people with a workplace pension are in a ‘gold-plated’ defined benefit (DB) scheme, which will guarantee a certain level of income in retirement based on their salary - employees aged 50 to 54 are the most likely to be in a DB pension scheme.
Jamie Jenkins, director of policy and external affairs at Royal London, said: "While we see high levels of participation for full-time staff, more needs to be done to boost the numbers of part-time workers in workplace pensions."
He continued: "Similarly, contribution rates to private sector, predominantly defined contribution schemes, continue to lag significantly behind their public sector counterparts, who are more likely to have defined benefit schemes.
"If we want to see people retiring well with their defined contribution pensions then we need to see further action to boost minimum contribution rates."
Tim Gosling, head of policy at the People's Pension, said: "One of the most effective ways of ensuring more part-time workers have the option of saving into a pension would be lowering the earnings threshold for automatic enrolment from £10,000 a year to £6,240."
Sarah Coles, personal finance analyst at Hargreaves Lansdown, said: "Putting people into workplace pensions automatically has been an incredible success, but there are still enormous numbers of people who fall through the cracks. Far fewer part-time workers are in their pension scheme, partly because more of them earn below the minimum threshold.
"Then there are those who are too young to qualify, and self-employed people who fall out of the system entirely.”
There's also a risk that those who have joined their workplace pension schemes aren't paying in anywhere near enough.
The statutory minimums on these pensions mean overall 8 per cent, of eligible salary, has to go into the pension, with employers paying at least 3 per cent.
Typically, employers are paying 2 per cent to 4 per cent and employees 4 per cent to 5 per cent, so plenty of employees will be getting combined contributions way below the level they need for a comfortable income in retirement in comparison to defined benefit schemes where typically the employee pays in 7 per cent or more and the employer 20 per cent or more.
Ms Coles said those receiving the minimum amounts into their pension should check whether their employer will match it if they increase their contributions.
She suggested: "Even if they don't match contributions, use a pension calculator to see what you should be paying in at this stage to hit your targets. Then go back to your household budget and see whether you can free up any more cash to boost contributions.”
A Department for Work and Pensions spokesperson said: "Automatic enrolment has been an extraordinary success, with over 10 million workers enrolled into a workplace pension to date and an additional £22.7 billion per year being saved compared to 2012 among eligible employees.
"The [UK] Government's ambition for the future of automatic enrolment will enable people to save more and to start saving earlier by abolishing the lower earnings limit for contributions and reducing the age for being automatically enrolled to 18 in the mid-2020s.
"Right now we're delivering our plan to create and protect jobs to help people secure their financial stability today, helping them plan for tomorrow and the retirement they want."
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