Almost a quarter of all single female pensioners live in poverty, a study has found.
The report, by charity Age Concern and equal rights organisation the Fawcett Society, found that, on average, women receive far lower pensions than men.
The study concluded that the pay gap which already exists between men and women during their working lives becomes a vast pension gulf in later life.
And the report's authors blamed a large part of female pensioner poverty on the way the state pension system works.
The study found that some women have to live on a reduced income on retirement because they took time off work to bring up children and therefore did not make sufficient National Insurance contributions to qualify for the full state pension.
In some cases, women opted for the reduced-rate 'married woman's stamp' National Insurance contributions in the 1960s and 1970s.
In return for lower contributions, they waived their right to the basic state pension until their husband reached 65, when they would receive 60% of his pension.
The report concluded that the state pension system was "outdated" and "littered with obstacles for women trying to build up a pension in their own right".
What is more, many women have traditionally worked in jobs which do not come with high value occupational pensions.
The report found that women got just 32p for every £1 of income received by men in a pensioner couple.
In order to address the gender wealth imbalance in retirement the report's authors proposed a number of measures.
Last December the government announced in its pension green paper plans to offer incentives to workers who choose to work on beyond the age of 65.
The introduction of a better and more flexible system of state pension credits for those who care for children or older people.
A guarantee that every woman - whether in employment, caring or unable to work for reasons such as a disability - receives a decent state pension that covers basic costs and is free of a means-test.
Better financial education and information to try and close the advice gap.
Better opportunities for women to build-up higher value company and personal pensions
However, radical reform of the state pension was not touched upon.
"The current state pension system is not working for women as it is based on the old assumption of men as the breadwinners and women as stay-at-home carers," said Katherine Rake, director of the Fawcett Society.