The pensions gap between the sexes has narrowed over the past few years but not as a result of a rise in female incomes, a survey from financial service group Prudential has revealed.

Rather than women’s pensions increasing in value, the difference has decreased because men’s incomes have fallen.

The survey showed that women will have an average of £12,250 income a year upon retirement, compared with £18,000 for men, meaning the gender gap has reduced to £5,750 from £7,400 in 2011.

The average pension for men and women overall has dropped to £15,500, compared with £16,600 in 2011.

In 2010, average male pension earnings were £19,600, with women retiring on around £12,200 a year, indicating little change compared with the income predicted for 2012.

Low interest rates and falling stock market values have hit pension earnings, while annuity incomes, which come from policies pensioners buy to secure a fixed income for the rest of their lives, have also dropped dramatically in the past four years.

For example, a 65-year-old man with a £100,000 pension plan can now buy an annuity paying about £6,000 a year, which is about 20 per cent less than he would have had in 2008.

Falling pension incomes could make it harder for employers to communicate the benefits of a pension or sign staff up to their company scheme.

Meanwhile, an ongoing negative view of the value of pensions could also undermine government efforts to get more people saving for old age.

The government's National Employment Savings Trust (Nest) scheme was set up to address a market failure in the pensions industry that left many employers and employees unable to access low-cost, good quality pension provision.