Graduates repay 9% of the amount earned above the threshold outlined in their plan.
They do not have to start making payments until the April after leaving their course and payments are made automatically through the tax system.
But Lewis said there was growing anger, particularly among those in England and Wales with Plan 2 loans, because recent higher inflation has resulted in increased interest rates being applied to the loans.
“When we’ve had high inflation, their interest rates have gone up and that has been particularly painful,” Lewis said.
And even though those rates have come down a little, Lewis pointed out, people who took out student loans during this period will have “a lot more” added on top “which makes it more difficult”.
Plan 2 loans are charged a rate of interest equal to Retail Prices Index (RPI) inflation, plus up to 3% on top based on earnings. Someone earning £51,245 or more with a Plan 2 loan will currently be charged 6.2%.
By contrast, those with Plan 1 and Plan 5 loans, who started university before 2012 and since 2023 respectively, are currently charged 3.2%.
While a higher interest rate does not affect the amount someone repays each month, it makes it harder to reduce the size of the loan, meaning the borrower could repay more over time.
The freeze on student loans came at the same time Reeves announced she would be extending the Conservative-initiated freeze on income tax and National Insurance thresholds for another three years.
When those thresholds are frozen, more income is taxed at higher rates as someone’s earnings rise, a process known as fiscal drag.
Plan 2 loans were introduced from 2012, at the same time the Conservative-Liberal Democrat coalition government tripled tuition fees to up to £9,000 a year.