More than half a million workers retiring before state pension age will have the chance to boost their pension at "bargain rates" over the coming five years, according to analysis.
Royal London found hundreds of thousands of teachers, nurses, civil servants and local government workers could benefit from opportunities to boost their state pension.
They can do this by paying heavily subsidised voluntary national insurance (NI) contributions for the years between the date when they retire and the date when they reach state pension age.
The calculations have been made to coincide with a new guide from Royal London, called "good with your money". The guide explains the new state pension and the options for existing pensioners to top up their state pension.
Under the new state pension system introduced earlier this year, people will generally be entitled to the full rate of £155.65 per week if they have 35 years of qualifying NI contributions.
But those who were members of public sector pension schemes or the pension schemes of many large employers generally paid a reduced rate of NI contributions, because their scheme was "contracted out".
These workers have a deduction made from their new state pension - which means they may not get the new full pension rate in the early years of the new system.
Former pensions minister Steve Webb, who is now policy director at Royal London, said many of these workers may be able to pay voluntary NI contributions to make up some of the shortfall in their state pension created by the years when they were contracted out.
Mr Webb said a single year of voluntary or "class 3" NI contributions can be bought for a lump sum of around £733.
This will boost someone's state pension entitlement by around £230 per year for the rest of their life. Based on a 20-year retirement, a lump sum of £733 could generate £4,600 in extra state pension over the course of someone's retirement.
And someone who filled five "missing" years in their NI contribution record could potentially receive an extra £23,000 in pension over their retirement for an outlay of less than £4,000.
Mr Webb said this could be of particular relevance to many public sector workers such as teachers, nurses and civil servants who are entitled to draw their occupational pension at 60 but will not get a state pension until they are 65 or 66.
If they retired at 60, they would not normally pay any further NI contributions between retirement and state pension age - but they could pay voluntary contributions for each of those years and generate a substantial return on these extra payments when they start to receive their state pension.
Based on analysis of the annual reports of large public sector pension schemes, Royal London estimates over half a million public sector workers could be in a position to benefit over the next five years, as well as many thousands of former private sector workers whose company pension scheme allowed them to draw a pension before state pension age.
The estimate includes around 210,000 NHS workers, around 150,000 teachers and around 130,000 civil service workers.
Mr Webb said it is "rare" for the Government to offer something on such generous financial terms.
He said: "Large numbers of workers could gain a substantial boost to their state pension for the payment of a relatively modest lump sum."
The guide to topping up a state pension is available at www.royallondon.com/goodwithyourmoney.
Pensions Minister Richard Harrington said that for people wondering about their options, there is a "wealth of information" on the gov.uk website.
He said: "Anyone looking to explore their options should go there as their first port of call."