Individuals retiring this year will receive an income 7.9% lower than those who retired in 2014, according to research.
Financial website Moneyfacts said this was due to change in the value of pension pots and a "sharp drop" in annuity rates offered.
Based on a monthly contribution of £100 over a period of 20 years, those who retired in September last year would have accrued a total pension fund of £44,089, and with an average annuity rate of £520 per £10,000 they would receive £2,292 per year.
Based on the same monthly contribution, Moneyfacts said those retiring this year would earn a pension fund of £42,442 with an annuity rate of £497 per £10,000, equating to an annual income of £2,109. The figure represents a fall of 7.9%.
Annuity income has also dropped by 72.7% over 15 years. Those who retired in September 2000 would have built up a pot of £89,366 with the same monthly contribution. The website said rates of £867 per £10,000 at the turn of the millennium were "far more favourable", leaving a retirement income of £7,748 per year.
Moneyfacts said with poor investment returns and falling annuity rates, even a monthly contribution of £300 would not be enough to achieve the same income as those who retired in 2000. For those retiring this year, a £300 monthly contribution would mean a larger pension pot of £127,322, but the rate of £497 per £10,000 would leave a retirement income of £6,327.
Richard Eagling, editor of investment life and pensions at Moneyfacts, said savers would need to make up the pension shortfall through greater contributions, or delay their retirement.
"It is vital to increase awareness not only of pension options, but also the potential retirement income outcomes, as too many people have outdated and unrealistic expectations as to what they will eventually receive," he said.
Meanwhile, a study carried out by Deloitte has found savers will have to find on average an additional £10,000 per year between now and retirement to meet an anticipated "savings gap" of £352bn - a gap between retirement income and needs - in 2050.
The firm said the savings gap could reach £352bn, up from an estimated £250bn today, nearly £32bn more than the consultancy estimated five years ago.
It said the reasons for the widening savings deficit include the UK population rising to 77 million adding £43bn, the gradual closure of defined benefit schemes costing £23 billion, and the rising cost of health care, expected to be £36 billion.
Andrew Power, investment management partner at Deloitte, said: "Despite welcome efforts by the government to tackle the savings gap through auto-enrolment and raising the pensions age, challenges still exist. People are living longer; many would rather spend today rather than save for tomorrow; and few know how much they actually have tucked away. Separately, the government is no longer as generous with tax incentives. As a result, we've seen significant changes in pensions over the last year."
Power said to achieve a particular standard of living at retirement people would need a "greater awareness of what must be saved today".