Members of Parliament will debate the proposed increase to the women's pension age today in the House of Commons.
Under government proposals, the age women are entitled to start receiving their state pension will go up from age 60 to 65 by 2018 and then both the male and female pension age will rise to 66 by 2020.
The accelerated increase has been criticised by pensions campaigners and MPs alike.
Ros Altmann, director-general of Saga, is asking both women and men to sign Saga's petition against the plans.
"We have so many women who are saying 'we have never been so angry, we cannot believe the government has let us down and in fact they are saying we will never vote for either the Tories or Lib Dems again because they have lied to us. They promised us in the coalition that they wouldn't do this and suddenly they are imposing it on us'," says Altmann.
More than half a million women already aged over 55 could face a shortfall of more than £10,000 each into their retirement income, according to Saga.
For more read: Women hit hardest by state pension changes
There are also concerns that many women are unaware of the pension reforms and still expect to collect their state pension at age 60. A survey by the charity Age UK reveals that thousands of women don't know the state retirement age has changed. It also reveals that 68% of women are worried about the plans.
"The government is asking people to plan their retirement, but it's difficult to see how women can plan properly when the government keeps moving the state pension age goalposts," says Michelle Mitchell, charity director at Age UK.
She says many women, facing the increase have either worked in low-paid jobs all their lives, had to stop working due to health problems or to care for others and have relied on receiving the pension at an earlier age.
"They have already had their state pension age changed once and this latest proposed change is one step too far by this government. Telling these women, at short notice, that they now have to wait up to another two years to collect their state pension is unfair."