Moving goalposts: women claim they weren't properly warned of having to wait up to six years longer to receive their state pension - Clara Molden

The Government has saved more than £5bn as a result of raising the age at which women start receiving their state pension, a new report has found.

The figure - which has been calculated by the authoritative think tank the Institue of Fiscal Studies - is the first to attempt to quantify the benefit to the Exchequer of making a cohort of women wait as long as six years for their state pension.

It will fuel the anger of those women, born in the Fifties, who claim they were not given adequate warning of the change. Many say they have been unable to prepare for the delay in receiving a retirement income from the state.

Moves to bring women's state pension age into line with men's began in 1995, based on an argument that women's greater average longevity meant they should not be claiming the state pension earlier than their male counterparts.

Women had been able to receive their state pension at 60, and the initial plans were to raise this to 65 over a ten-year period beginning in 2010.

However, the Coalition Government then accelerated this timetable in 2011. This infuriated many and led to the formation of the protest group Waspi (Women Against State Pension Increases), who argued they were not warned of the changes.

The IFS now calculates that from the year 2015-16 the Government is making savings of £5.1bn, at the expense of 1.1 million women who are worse off by an average of £32 a week.

These households are receiving about £74 a week less in state pensions and other state benefits, but for women aged 60 to 62 it has led to increased employment rates - making them £2.5bn better off. The net impact has been that these households lose out on £32 a week.

Jonathon Cribb, a senior researcher at the influential think tank, said: "The increased state pension age is boosting employment – and therefore earnings – of affected women, but this is only partially offsetting reduced incomes from state pensions and other benefits.

"Since both rich and poor women are losing out by, on average, roughly similar amounts, the reform increases income poverty rates among households containing a woman who has reached age 60 but has not yet reached her state pension age."

He added: "It is important that the Government communicates the ongoing increases in the state pension age clearly so that families can plan for their retirement as well as possible."

Commentators were quick to point out that the worst affected households would be those where women could not work because, for example, they were required to care for a partner or parent.

sam.meadows@telegraph.co.uk