The Prime Minister has become embroiled in the row over raising the state pension age (SPA) for women.
Under current proposals, the SPA will reach 66 by 2020 instead of the previous staging date of 2026.
This means female SPA will rise by six years in 2020 as opposed to one year for men and around 300,000 women in their fifties will have to wait up to two years longer to claim their pensions.
Pressure has been growing for the government to make changes to the Pensions Bill, which includes draft legislation on women's SPA, but Cameron defended the policy.
He said: "The key fact is 85% of the women affected are going to lose one year or less in terms of their pension.
"Because we have linked the pension to earnings, people who retire today will be £15,000 better off than they were under the policies of the last government."
In May, pensions minister Steve Webb said the government would "reflect" on how its plans affect women in response to union anger.
In the past week, six more MPs have signed up to an early day motion (EDM) calling on the government to reconsider its plans.
At present, 168 MPs have signed the EDM, including one third of all Liberal Democrats.
A date still has not been set for the second reading of the bill although shadow pensions minister Rachel Reeves said the reading was expected weeks ago.
She suggested the delay is due to opposition to the SPA rise, and added Labour is attempting to bring Liberal Democrats onside to defeat the SPA clause.
However, Jennie Kreser, pensions partner at Silverman Sherliker said any attempt to reduce the impact on women by the Department for Work and Pensions will be struck down by the Treasury.
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