The TUC has urged the government to freeze the lower thresholds in the auto-enrolment regime - keeping the bottom of the earnings band on which contributions have to be paid (£5,564) and the earnings level at which auto-enrolment is triggered (£7,475) - at their current levels.

The government is set to introduce a new earnings trigger for auto-enrolment, following their review, which recommended that workers should only be auto-enrolled once their earnings rose above the income tax threshold (£7,475). They would still pay contributions from the bottom of the earnings band.

However, the TUC argues that women would be the main losers from the new earnings trigger as the vast majority of workers with pay between the lower limit of the earnings band and the income tax threshold are women working part-time. The auto-enrolment trigger should therefore be frozen, says the TUC.

The TUC believes that linking auto-enrolment with the income tax threshold is particularly damaging given the coalition plans to increase it to £10,000.

A TUC analysis of official earnings data shows that the new earnings trigger could eventually stop around two million women from being auto-enrolled into pensions.