The union has joined calls from the pensions industry asking government to abolish the current auto-enrolment earnings trigger, set at £10,000.
The earnings trigger indirectly discriminates against women by disproportionately excluding them from access to occupational pension schemes, it said.
In its review of auto-enrolment in December, the DWP announced that the minimum age for workers to be included in workplace pension schemes will be reduced from 22 to 18-years-old, and that it will change the way pension contributions are calculated by the mid 2020s.
"It was a great disappointment that the government did not take the opportunity to abolish the earnings trigger," Prospect stated.
Finally, the union is also calling on the government to give state pension credits to people who opt out of receiving child benefit and to solve the pension tax relief loophole which leaves low earners in net pay schemes missing out on the tax break.
maria.espadinha@ft.com