Labour MP Luke Akehurst called the issue an “injustice” which not only affected Nissan employees, but other members of direct benefit schemes across the country.
“Each year they find that because the cost of living is going up, they haven’t got the income that they need in retirement,” he said.
“There’s a particular unfairness that as people get deeper into their time of retirement, their disposable income is less and less keeping pace with inflation.”
A Nissan spokesperson said: “By nature, discretionary increases are not guaranteed and any decision that the trustees make on it must take into account all relevant factors.”
Akehurst said he planned to put pressure on the government to change the pre-1997 law.
The Department for Work and Pensions (DWP) said it was working on pension reforms which included giving trustees of well-funded defined benefit schemes more flexibility to negotiate improvements for members.