Millions of women will now lose out on their full state pension after the government quietly reneged on a deal that would have allowed them to access full payment.
It emerged last night that ministers have dropped plans to allow women who have taken time out of work to top-up their national insurance (NI) contributions with lump-sum payments.
Only three in ten of the 12 million women over 45 have made sufficient NI payments to qualify for a full state pension on retirement.
Six months ago the government indicated it would support measures that would allow nearly 8.5 million women to claim a full state pension by making up shortfalls in their NI contributions.
The Conservatives last night attacked the government's "U-turn" while campaigners warned it risked condemning women to pensioner poverty.
An amendment to allow lump sum NI payments was introduced to the pensions bill by Baroness Hollis and received provisional government support.
This week, however, after requesting a ministerial update, Baroness Hollis was told the government was abandoning the scheme.
Lord Oakeshott, the Lib Dem pension spokesman, said: "When the U-turn was announced you could see a wave of revulsion sweep around the House.
"Gordon Brown should be ashamed of himself for sneaking this out just before Christmas.
"He must have a heart of stone to do this to millions of women and carers who had had their hopes raised by the government that they could buy back missing years which stopped them qualifying for a full pension."
Shadow work and pensions secretary Chris Grayling said the move was a "betrayal of stay-at-home-mums".
Mr Grayling explained: "This is a massive U-turn.
"In the summer, pensions minister Mike O'Brien was very ready to make all the right noises for the women concerned but when it comes to a decision not to do something, it is slipped out at the end of the parliamentary session when nobody has noticed."
Age Concern argued the move risked condemning more women to poverty.
Michelle Mitchell, a spokeswoman for the charity, said: "This is a slap in the face for thousands of women in or approaching retirement who are being penalised for taking time out of work to care."
The Department for Work and Pensions maintains women who miss out on a full state pension can apply for pensions credit. However, take-up is historically low of this means-tested benefit.