Women from across the country converged on Parliament today to call on MPs to vote against changes that will make them wait longer before they can claim their state pension.
Around 150 women took part in the event, which was organised by Age UK, to urge the Government not to "move the pensions goal posts again".
The charity warned that the Government's plan to raise the state pension age to 66 by 2020 - six years earlier than previously planned - does not give people enough time to plan and risks plunging thousands of women into poverty.
Around 2.6 million women will have to wait at least one year longer for their state pension as a result of this change and plans to accelerate the rate at which women's state pension age is increased to 65 in line with men's.
Among these, 330,000 women will have to wait an extra 18 months to two years before they can start drawing the benefit.
The 33,000 women who will be hardest hit and have to wait two years will lose an average of £10,000 of state pension income.
It is also the second time that these women have seen the age at which they can claim their state pension increased, after the previous government set in place plans to raise it to 65 by 2020.
Age UK warned that many of the women affected by the changes are either carers or in poor health, meaning that working for longer is not an option for them.
Speaking at the event, an Age UK spokeswoman said: "MPs are coming out and talking to the women and listening to their concerns.
"We are very hopeful that it is going to make a difference and people will understand that this change will impact on women really badly."
Jenny Willott, the co-chair of the Liberal Democrat Parliamentary Committee on Work and Pensions, said: "There is real and justified concern that the changes to the state pension age are deeply unfair, particularly to the 33,000 women who are being asked to work two years longer at very short notice and without time to plan properly for their retirement.
"I agree with the Age UK protesters: these changes should be reconsidered. The Government needs to look at how to change the current plan to make it fairer to women."
She added that she would be raising her concerns with the Deputy Prime Minister and the pensions minister and urging them to rethink the plans.
An early day motion calling for the increase in the state pension age to be delayed has been signed by 154 MPs, including a number of Conservatives and Liberal Democrats.
Over-50s group Saga said it had been inundated with letters and emails from women who were "distraught and angry" about having to wait longer before they could claim their state pension, while 20,000 people have signed a petition on the issue.
A Department for Work and Pensions spokeswoman said: "In a country where 10 million of us will live to be 100, we simply can't go on paying the state pension at an age that was set early in the last century.
"Although women will experience the rise in the state pension age more quickly than previously planned, they will still draw the state pension for an average of 23 years.
"Our 'triple guarantee' means someone retiring today on a full basic State Pension will receive £15,000 more over their retirement than they would have done under the old prices link."