Government plans to make women wait longer for their state pension will be debated by MPs later today.
The proposed changes to the Pensions Bill would see the entitlement age for women rising from 60 to 65 by 2018.
The plan is then to increase this to 66 for both sexes by the year 2020.
Critics say that such changes will have a disproportionate impact on women currently in their late 50s, who will be forced to keep working longer.
But despite looking at ways of easing the transition, ministers say that the changes are likely to go ahead.
A spokesman for the Department for Work and Pensions said that delaying the move to 66 "would cost the taxpayer £10bn and would be an unfair burden on the next generation."
The previous Labour government had agreed to achieve equalisation of the entitlement age at 65 by April 2020, but the coalition's plans intend to see it reached by November 2018.
More than 170 MPs, including both Conservative and Liberal Democrat backbenchers, have signed a Commons motion calling for a rethink over the plans, which are being called unfair for the 330,000 women who will have to wait between 18 months and two years longer for their pensions.
Rachel Reeves, shadow pensions minister, said it was "simply wrong to punish women by moving the goal posts at this late stage."