The firm, formerly B&CE Pensions, provides the People’s Pension to more than 6.5m people in the UK.

Its research showed that 72% of people who had recently transferred their pension did not know the exact fees for their old pension or what they were being charged for their new one.

The firm said the pension industry needed to be more transparent and should help savers understand key information when transferring their pension to prevent them from making detrimental financial decisions.

Patrick Heath-Lay, chief executive at People’s Partnership, said: “If people can’t make an informed decision about the value they are being offered by different providers, they risk losing thousands of pounds from their retirement pots. This lack of transparency is an enormous issue that pensions providers have to address.”

He added: “While there are many factors that can make a pension attractive, the two fundamental aspects are investment returns and charges.”

The firm's analysis showed that for a 30-year-old earning £30,000, moving a £10,000 pension pot from a provider charging 0.4% to one charging 0.75%, would leave them £32,834 worse off when they retired at 67.

If they moved a £50,000 pot, they would have £59,523 less to live on in retirement. And if the same person was earning £45,000 and moved a £50,000 pension, they would be £72,689 worse off in retirement.

The calculations are based on a 30-year-old who begins taking their pension in 2061. Total contributions are 8% and wage inflation is 3.5%. Investment returns are 5% (2.5% return and 2.5% inflation). The figures used for charges are reflective of current providers in the marketplace.

Mr Heath-Lay said: "The real-world impact of small differences in percentages are incredibly hard to grasp, so the onus is on the pension industry to make sure consumers understand what they are being charged."

• The research was conducted in November and December 2023 by People’s Partnership. It surveyed 1,000 people who had consolidated their defined contribution pensions, without the help of a financial adviser, in the last two years.